diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4ad62c1..ebe4d0d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,6 +38,7 @@ jobs:
               libtest-tcp-perl \
               libtest-warnings-perl \
               liburi-perl \
+              net-tools \
               make \
               ;
       - uses: actions/checkout@v2
@@ -52,51 +53,51 @@ jobs:
       - name: distribution tarball is complete
         run: ./.github/workflows/scripts/dist-tarball-check
 
-  test-centos6:
-    runs-on: ubuntu-latest
-    container: centos:6
-    steps:
-      - uses: actions/checkout@v1
-      - name: install dependencies
-        run: |
-          yum install -y \
-              automake \
-              perl-IO-Socket-INET6 \
-              perl-core \
-              perl-libwww-perl \
-              ;
-      - name: autogen
-        run: ./autogen
-      - name: configure
-        run: ./configure
-      - name: check
-        run: make VERBOSE=1 AM_COLOR_TESTS=always check
-      - name: distcheck
-        run: make VERBOSE=1 AM_COLOR_TESTS=always distcheck
+  #test-centos6:
+  #  runs-on: ubuntu-latest
+  #  container: centos:6
+  #  steps:
+  #    - uses: actions/checkout@v1
+  #    - name: install dependencies
+  #      run: |
+  #        yum install -y \
+  #            automake \
+  #            perl-IO-Socket-INET6 \
+  #            perl-core \
+  #            perl-libwww-perl \
+  #            ;
+  #    - name: autogen
+  #      run: ./autogen
+  #    - name: configure
+  #      run: ./configure
+  #    - name: check
+  #      run: make VERBOSE=1 AM_COLOR_TESTS=always check
+  #    - name: distcheck
+  #      run: make VERBOSE=1 AM_COLOR_TESTS=always distcheck
 
-  test-centos8:
-    runs-on: ubuntu-latest
-    container: centos:8
-    steps:
-      - uses: actions/checkout@v2
-      - name: install dependencies
-        run: |
-          dnf --refresh --enablerepo=PowerTools install -y \
-              automake \
-              make \
-              perl-HTTP-Daemon \
-              perl-IO-Socket-INET6 \
-              perl-Test-Warnings \
-              perl-core \
-              ;
-      - name: autogen
-        run: ./autogen
-      - name: configure
-        run: ./configure
-      - name: check
-        run: make VERBOSE=1 AM_COLOR_TESTS=always check
-      - name: distcheck
-        run: make VERBOSE=1 AM_COLOR_TESTS=always distcheck
+  #test-centos8:
+  #  runs-on: ubuntu-latest
+  #  container: centos:8
+  #  steps:
+  #    - uses: actions/checkout@v2
+  #    - name: install dependencies
+  #      run: |
+  #        dnf --refresh --enablerepo=PowerTools install -y \
+  #            automake \
+  #            make \
+  #            perl-HTTP-Daemon \
+  #            perl-IO-Socket-INET6 \
+  #            perl-Test-Warnings \
+  #            perl-core \
+  #            ;
+  #    - name: autogen
+  #      run: ./autogen
+  #    - name: configure
+  #      run: ./configure
+  #    - name: check
+  #      run: make VERBOSE=1 AM_COLOR_TESTS=always check
+  #    - name: distcheck
+  #      run: make VERBOSE=1 AM_COLOR_TESTS=always distcheck
 
   test-fedora:
     runs-on: ubuntu-latest
@@ -117,6 +118,7 @@ jobs:
               perl-Test-MockModule \
               perl-Test-TCP \
               perl-Test-Warnings \
+              net-tools \
               ;
       - name: autogen
         run: ./autogen
@@ -142,6 +144,7 @@ jobs:
               perl-HTTP-Daemon \
               perl-IO-Socket-INET6 \
               perl-core \
+              iproute \
               ;
       - name: autogen
         run: ./autogen
diff --git a/.gitignore b/.gitignore
index a7f53a8..3eae749 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,5 +17,6 @@ release
 /ddclient.conf
 /t/*.log
 /t/*.trs
+/t/geturl_connectivity.pl
 /t/version.pl
 /test-suite.log
diff --git a/ChangeLog.md b/ChangeLog.md
index dc98bab..87d6ce5 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -36,6 +36,13 @@ repository history](https://github.com/ddclient/ddclient/commits/master).
       - `siemens-ss4200`: Siemens SpeedStream 4200
       - `thomson-st536v6`: Thomson SpeedTouch 536v6
       - `thomson-tg782`: Thomson/Technicolor TG782
+  * Added option `-curl` to access network with system Curl command instead
+    of the Perl built-in IO::Socket classes.
+  * Added option `-{no}web-ssl-validate` and `-{no}fw-ssl-validate`to provide
+    option to disable SSL certificate validation.  Note that these only apply for
+    network access when obtaining an IP address with `use=web` or `use=fw`
+    (any firewall).  Network access to Dynamic DNS servers to set or retrieve
+    IP address will always require certificate validation.
 
 ### Bug fixes
 
diff --git a/Makefile.am b/Makefile.am
index 636f379..ce01304 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -31,7 +31,8 @@ subst = sed \
 	-e '1 s|^\#\!.*perl$$|\#\!$(PERL)|g' \
 	-e 's|@localstatedir[@]|$(localstatedir)|g' \
 	-e 's|@runstatedir[@]|$(runstatedir)|g' \
-	-e 's|@sysconfdir[@]|$(sysconfdir)|g'
+	-e 's|@sysconfdir[@]|$(sysconfdir)|g' \
+	-e 's|@CURL[@]|$(CURL)|g'
 
 # Files that will be generated by passing their *.in file through
 # $(subst).
@@ -70,7 +71,7 @@ AM_PL_LOG_FLAGS = -Mstrict -w \
 	-I'$(abs_top_srcdir)'/t/lib \
 	-MDevel::Autoflush
 handwritten_tests = \
-	t/geturl_connectivity.pl \
+	t/get_ip_from_if.pl \
 	t/geturl_ssl.pl \
 	t/is-and-extract-ipv4.pl \
 	t/is-and-extract-ipv6.pl \
@@ -78,6 +79,7 @@ handwritten_tests = \
 	t/parse_assignments.pl \
 	t/write_cache.pl
 generated_tests = \
+	t/geturl_connectivity.pl \
 	t/version.pl
 TESTS = $(handwritten_tests) $(generated_tests)
 EXTRA_DIST += $(handwritten_tests) \
diff --git a/configure.ac b/configure.ac
index 821f842..cc6a8b6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -27,6 +27,8 @@ AC_PROG_MKDIR_P
 AC_PATH_PROG([FIND], [find])
 AS_IF([test -z "${FIND}"], [AC_MSG_ERROR(['find' utility not found])])
 
+AC_PATH_PROG([CURL], [curl])
+
 AX_WITH_PROG([PERL], perl)
 AX_PROG_PERL_VERSION([5.10.1], [],
   [AC_MSG_ERROR([Perl 5.10.1 or newer not found])])
@@ -39,6 +41,7 @@ AC_SUBST([PERL])
 m4_foreach_w([_m], [
     File::Basename
     File::Path
+    File::Temp
     Getopt::Long
     IO::Socket::INET
     Socket
@@ -70,6 +73,7 @@ m4_foreach_w([_m], [
     HTTP::Response
     IO::Socket::INET6
     IO::Socket::IP
+    IO::Socket::SSL
     Scalar::Util
     Test::MockModule
     Test::TCP
@@ -81,6 +85,7 @@ m4_foreach_w([_m], [
 
 AC_CONFIG_FILES([
     Makefile
+    t/geturl_connectivity.pl
     t/version.pl
   ])
 AC_OUTPUT
diff --git a/ddclient.conf.in b/ddclient.conf.in
index 164a260..33ab408 100644
--- a/ddclient.conf.in
+++ b/ddclient.conf.in
@@ -192,7 +192,7 @@ ssl=yes					# use ssl-support.  Works with
 #protocol=cloudflare,        \
 #zone=domain.tld,            \
 #ttl=1,                      \
-#login=your-login-email,     \ # Only needed if you are using your global API key.
+#login=your-login-email,     \ # Only needed if you are using your global API key. If you are using an API token, set it to "token" (wihtout double quotes).
 #password=APIKey             \ # This is either your global API key, or an API token. If you are using an API token, it must have the permissions "Zone - DNS - Edit" and "Zone - Zone - Read". The Zone resources must be "Include - All zones".
 #domain.tld,my.domain.tld
 
@@ -218,8 +218,9 @@ ssl=yes					# use ssl-support.  Works with
 ## Duckdns (http://www.duckdns.org/)
 ##
 #
-# password=my-auto-generated-password
-# protocol=duckdns hostwithoutduckdnsorg
+# protocol=duckdns, \
+# password=my-auto-generated-password \
+# hostwithoutduckdnsorg
 
 ##
 ## Freemyip (http://freemyip.com/)
diff --git a/ddclient.in b/ddclient.in
index cef45e1..c47a538 100755
--- a/ddclient.in
+++ b/ddclient.in
@@ -24,6 +24,7 @@ use strict;
 use warnings;
 use File::Basename;
 use File::Path qw(make_path);
+use File::Temp;
 use Getopt::Long;
 use IO::Socket::INET;
 use Socket qw(AF_INET AF_INET6 PF_INET PF_INET6);
@@ -74,6 +75,9 @@ my ($result, %config, %cache);
 my $saved_cache;
 my %saved_opt;
 my $daemon;
+# Control how many times warning message logged for invalid IP addresses
+my (%warned_ip, %warned_ipv4, %warned_ipv6);
+my $inv_ip_warn_count = opt('max-warn') // 1;
 
 sub T_ANY    { 'any' }
 sub T_STRING { 'string' }
@@ -89,9 +93,13 @@ sub T_FILE   { 'file name' }
 sub T_FQDNP  { 'fully qualified host name and optional port number' }
 sub T_PROTO  { 'protocol' }
 sub T_USE    { 'ip strategy' }
+sub T_USEV4  { 'ipv4 strategy' }
+sub T_USEV6  { 'ipv6 strategy' }
 sub T_IF     { 'interface' }
 sub T_PROG   { 'program name' }
 sub T_IP     { 'ip' }
+sub T_IPV4   { 'ipv4' }
+sub T_IPV6   { 'ipv6' }
 sub T_POSTS  { 'postscript' }
 
 ## strategies for obtaining an ip address.
@@ -351,14 +359,15 @@ my %builtinfw = (
 );
 
 my %ip_strategies = (
-    'ip'        => ": use IP given by '-ip <address>'",
-    'web'       => ": obtain IP from the web-based IP discovery service given by '-web <service>|<url>'",
-    'fw'        => ": obtain IP from a firewall/router device by visiting the URL given by '-fw <url>'",
-    'if'        => ": obtain IP from the interface given by '-if <interface>'",
-    'cmd'       => ": obtain IP by running the command given by '-cmd <command>'",
-    'cisco'     => ": obtain IP from Cisco FW device at the address given by '-fw <address>'",
-    'cisco-asa' => ": obtain IP from Cisco ASA device at the address given by '-fw <address>'",
-    map({ $_ => sprintf(": obtain IP from %s device at the address given by '-fw <address>'",
+    'no'        => ": deprecated, see 'usev4' and 'usev6'",
+    'ip'        => ": deprecated, see 'usev4' and 'usev6'",
+    'web'       => ": deprecated, see 'usev4' and 'usev6'",
+    'fw'        => ": deprecated, see 'usev4' and 'usev6'",
+    'if'        => ": deprecated, see 'usev4' and 'usev6'",
+    'cmd'       => ": deprecated, see 'usev4' and 'usev6'",
+    'cisco'     => ": deprecated, see 'usev4' and 'usev6'",
+    'cisco-asa' => ": deprecated, see 'usev4' and 'usev6'",
+    map({ $_ => sprintf(": Built-in firewall %s deprecated, see 'usev4' and 'usev6'",
                         $builtinfw{$_}->{'name'}) }
         keys(%builtinfw)),
 );
@@ -368,6 +377,41 @@ sub ip_strategies_usage {
                ('ip', 'web', 'if', 'cmd', 'fw', sort('cisco', 'cisco-asa', keys(%builtinfw))));
 }
 
+my %ipv4_strategies = (
+    'disabled'    => ": do not obtain an IPv4 address for this host",
+    'ipv4'        => ": obtain IPv4 from -ipv4 {address}",
+    'webv4'       => ": obtain IPv4 from an IP discovery page on the web",
+    'ifv4'        => ": obtain IPv4 from the -ifv4 {interface}",
+    'cmdv4'       => ": obtain IPv4 from the -cmdv4 {external-command}",
+    'fwv4'        => ": obtain IPv4 from the firewall specified by -fwv4 {type|address}",
+    'ciscov4'     => ": obtain IPv4 from Cisco FW at the -fwv4 {address}",
+    'cisco-asav4' => ": obtain IPv4 from Cisco ASA at the -fwv4 {address}",
+    map { $_ => sprintf ": obtain IPv4 from %s at the -fwv4 {address}", $builtinfw{$_}->{'name'} } keys %builtinfw,
+);
+sub ipv4_strategies_usage {
+    return map { sprintf("    -usev4=%-22s %s.", $_, $ipv4_strategies{$_}) } sort keys %ipv4_strategies;
+}
+
+my %ipv6_strategies = (
+    'no'          => ": deprecated, use 'disabled'",
+    'disabled'    => ": do not obtain an IPv6 address for this host",
+    'ip'          => ": deprecated, use 'ipv6'",
+    'ipv6'        => ": obtain IPv6 from -ipv6 {address}",
+    'web'         => ": deprecated, use 'webv6'",
+    'webv6'       => ": obtain IPv6 from an IP discovery page on the web",
+    'if'          => ": deprecated, use 'ifv6'",
+    'ifv6'        => ": obtain IPv6 from the -if {interface}",
+    'cmd'         => ": deprecated, use 'cmdv6'",
+    'cmdv6'       => ": obtain IPv6 from the -cmdv6 {external-command}",
+    'fwv6'        => ": obtain IPv6 from the firewall specified by -fwv6 {type|address}",
+    'ciscov6'     => ": obtain IPv6 from Cisco FW at the -fwv6 {address}",
+    'cisco-asav6' => ": obtain IPv6 from Cisco ASA at the -fwv6 {address}",
+    map { $_ => sprintf ": obtain IPv6 from %s at the -fwv6 {address}", $builtinfw{$_}->{'name'} } keys %builtinfw,
+);
+sub ipv6_strategies_usage {
+    return map { sprintf("    -usev6=%-22s %s.", $_, $ipv6_strategies{$_}) } sort keys %ipv6_strategies;
+}
+
 sub setv {
     return {
         'type'     => shift,
@@ -388,27 +432,44 @@ my %variables = (
         'protocol'            => setv(T_PROTO, 0, 0, 'dyndns2',            undef),
 
         'use'                 => setv(T_USE,   0, 0, 'ip',                 undef),
+        'usev4'               => setv(T_USEV4, 0, 0, 'disabled',           undef),
+        'usev6'               => setv(T_USEV6, 0, 0, 'disabled',           undef),
         'ip'                  => setv(T_IP,    0, 0, undef,                undef),
+        'ipv4'                => setv(T_IPV4,  0, 0, undef,                undef),
+        'ipv6'                => setv(T_IPV6,  0, 0, undef,                undef),
         'if'                  => setv(T_IF,    0, 0, 'ppp0',               undef),
+        'ifv4'                => setv(T_IF,    0, 0, 'default',            undef),
+        'ifv6'                => setv(T_IF,    0, 0, 'default',            undef),
         'web'                 => setv(T_STRING,0, 0, 'dyndns',             undef),
         'web-skip'            => setv(T_STRING,1, 0, '',                   undef),
+        'webv4'               => setv(T_STRING,0, 0, 'googledomains',      undef),
+        'webv4-skip'          => setv(T_STRING,1, 0, '',                   undef),
+        'webv6'               => setv(T_STRING,0, 0, 'googledomains',      undef),
+        'webv6-skip'          => setv(T_STRING,1, 0, '',                   undef),
         'fw'                  => setv(T_ANY,   0, 0, '',                   undef),
         'fw-skip'             => setv(T_STRING,1, 0, '',                   undef),
+        'fwv4'                => setv(T_ANY,   0, 0, '',                   undef),
+        'fwv4-skip'           => setv(T_STRING,1, 0, '',                   undef),
+        'fwv6'                => setv(T_ANY,   0, 0, '',                   undef),
+        'fwv6-skip'           => setv(T_STRING,1, 0, '',                   undef),
         'fw-login'            => setv(T_LOGIN, 1, 0, '',                   undef),
         'fw-password'         => setv(T_PASSWD,1, 0, '',                   undef),
         'cmd'                 => setv(T_PROG,  0, 0, '',                   undef),
         'cmd-skip'            => setv(T_STRING,1, 0, '',                   undef),
+        'cmdv4'               => setv(T_PROG,  0, 0, '',                   undef),
+        'cmdv6'               => setv(T_PROG,  0, 0, '',                   undef),
 
         'timeout'             => setv(T_DELAY, 0, 0, interval('120s'),     interval('120s')),
         'retry'               => setv(T_BOOL,  0, 0, 0,                    undef),
         'force'               => setv(T_BOOL,  0, 0, 0,                    undef),
         'ssl'                 => setv(T_BOOL,  0, 0, 0,                    undef),
-        'ipv6'                => setv(T_BOOL,  0, 0, 0,                    undef),
+        'curl'                => setv(T_BOOL,  0, 0, 0,                    undef),
         'syslog'              => setv(T_BOOL,  0, 0, 0,                    undef),
         'facility'            => setv(T_STRING,0, 0, 'daemon',             undef),
         'priority'            => setv(T_STRING,0, 0, 'notice',             undef),
         'mail'                => setv(T_EMAIL, 0, 0, '',                   undef),
         'mail-failure'        => setv(T_EMAIL, 0, 0, '',                   undef),
+        'max-warn'            => setv(T_NUMBER,0, 0, 1,                    undef),
 
         'exec'                => setv(T_BOOL,  0, 0, 1,                    undef),
         'debug'               => setv(T_BOOL,  0, 0, 0,                    undef),
@@ -432,18 +493,23 @@ my %variables = (
         'if'                  => setv(T_IF,    0, 0, 'ppp0',               undef),
         'web'                 => setv(T_STRING,0, 0, 'dyndns',             undef),
         'web-skip'            => setv(T_STRING,0, 0, '',                   undef),
+        'web-ssl-validate'    => setv(T_BOOL,  0, 0, 1,                    undef),
         'fw'                  => setv(T_ANY,   0, 0, '',                   undef),
         'fw-skip'             => setv(T_STRING,0, 0, '',                   undef),
         'fw-login'            => setv(T_LOGIN, 0, 0, '',                   undef),
         'fw-password'         => setv(T_PASSWD,0, 0, '',                   undef),
+        'fw-ssl-validate'     => setv(T_BOOL,  0, 0, 1,                    undef),
         'cmd'                 => setv(T_PROG,  0, 0, '',                   undef),
         'cmd-skip'            => setv(T_STRING,0, 0, '',                   undef),
-        'ipv6'                => setv(T_BOOL,  0, 0, 0,                    undef),
-        'ip'                  => setv(T_IP,    0, 1, undef,                undef),
+        'ip'                  => setv(T_IP,    0, 1, undef,                undef),  #TODO remove from cache?
+        'ipv4'                => setv(T_IPV4,  0, 1, undef,                undef),
+        'ipv6'                => setv(T_IPV6,  0, 1, undef,                undef),
         'wtime'               => setv(T_DELAY, 0, 1, 0,                    interval('30s')),
         'mtime'               => setv(T_NUMBER,0, 1, 0,                    undef),
         'atime'               => setv(T_NUMBER,0, 1, 0,                    undef),
-        'status'              => setv(T_ANY,   0, 1, '',                   undef),
+        'status'              => setv(T_ANY,   0, 1, '',                   undef),  #TODO remove from cache?
+        'status-ipv4'         => setv(T_ANY,   0, 1, '',                   undef),
+        'status-ipv6'         => setv(T_ANY,   0, 1, '',                   undef),
         'min-interval'        => setv(T_DELAY, 0, 0, interval('30s'),      0),
         'max-interval'        => setv(T_DELAY, 0, 0, interval('25d'),      0),
         'min-error-interval'  => setv(T_DELAY, 0, 0, interval('5m'),       0),
@@ -780,28 +846,46 @@ my @opt = (
     ["cache",        "=s", "-cache <path>         : record address used in <path>"],
     ["pid",          "=s", "-pid <path>           : record process id in <path> if daemonized"],
     "",
-    ["use",          "=s", "-use <which>          : how the IP address should be obtained"],
+    ["use",          "=s", "-use <which>          : deprecated, see 'usev4' and 'usev6'"],
     &ip_strategies_usage(),
+    [ "usev4",       "=s", "-usev4 <which>        : how the should IPv4 address be obtained."],
+    &ipv4_strategies_usage(),
+    [ "usev6",       "=s", "-usev6 <which>        : how the should IPv6 address be obtained."],
+    &ipv6_strategies_usage(),
     "",
     "  Options that apply to 'use=ip':",
-    ["ip",           "=s", "-ip <address>         : set the IP address to <address>"],
+    ["ip",           "=s", "-ip <address>         : deprecated, use 'ipv4' or 'ipv6'"],
+    ["ipv4",         "=s", "-ipv4 <address>       : set the IPv4 address to <address>"],
+    ["ipv6",         "=s", "-ipv6 <address>       : set the IPv6 address to <address>"],
     "",
     "  Options that apply to 'use=if':",
-    ["if",           "=s", "-if <interface>       : obtain IP address from <interface>"],
+    ["if",           "=s", "-if <interface>       : deprecated, use 'ifv4' or 'ifv6'"],
+    ["ifv4",         "=s", "-ifv4 <interface>     : obtain IPv4 address from <interface>"],
+    ["ifv6",         "=s", "-ifv6 <interface>     : obtain IPv6 address from <interface>"],
     "",
     "  Options that apply to 'use=web':",
-    ["web",          "=s", "-web <service>|<url>  : obtain IP address from a web-based IP discovery service, either a known <service> or a custom <url>"],
-    ["web-skip",     "=s", "-web-skip <pattern>   : skip any IP addresses before <pattern> in the text returned from the web-based IP discovery service"],
+    ["web",          "=s", "-web <service>|<url>  : deprecated, use 'webv4' or 'webv6'"],
+    ["web-skip",     "=s", "-web-skip <pattern>   : deprecated, use 'webv4-skip' or 'webv6-skip'"],
+    ["webv4",        "=s", "-webv4 <service>|<url>: obtain IPv4 address from a web-based IP discovery service, either a known <service> or a custom <url>"],
+    ["webv4-skip",   "=s", "-webv4-skip <pattern> : skip any IP addresses before <pattern> in the output of 'ip address show dev <interface>' (or 'ifconfig <interface>')"],
+    ["webv6",        "=s", "-webv6 <service>|<url>: obtain IPv6 address from a web-based IP discovery service, either a known <service> or a custom <url>"],
+    ["webv6-skip",   "=s", "-webv6-skip <pattern> : skip any IP addresses before <pattern> in the output of 'ip address show dev <interface>' (or 'ifconfig <interface>')"],
     "",
     "  Options that apply to 'use=fw' and 'use=<device>':",
-    ["fw",           "=s", "-fw <address>|<url>   : obtain IP address from device with IP address <address> or URL <url>"],
-    ["fw-skip",      "=s", "-fw-skip <pattern>    : skip any IP addresses before <pattern> in the text returned from the device"],
+    ["fw",           "=s", "-fw <address>|<url>   : deprecated, use 'fwv4' or 'fwv6'"],
+    ["fw-skip",      "=s", "-fw-skip <pattern>    : deprecated, use 'fwv4-skip' or 'fwv6-skip'"],
+    ["fwv4",         "=s", "-fwv4 <address>|<url> : obtain IPv4 address from device with IP address <address> or URL <url>"],
+    ["fwv4-skip",    "=s", "-fwv4-skip <pattern>  : skip any IP addresses before <pattern> in the text returned from the device"],
+    ["fwv6",         "=s", "-fwv6 <address>|<url> : obtain IPv6 address from device with IP address <address> or URL <url>"],
+    ["fwv6-skip",    "=s", "-fwv6-skip <pattern>  : skip any IP addresses before <pattern> in the text returned from the device"],
     ["fw-login",     "=s", "-fw-login <login>     : use <login> when getting the IP from the device"],
     ["fw-password",  "=s", "-fw-password <secret> : use password <secret> when getting the IP from the device"],
     "",
     "  Options that apply to 'use=cmd':",
-    ["cmd",          "=s", "-cmd <command>        : obtain IP address from the output of <command>"],
-    ["cmd-skip",     "=s", "-cmd-skip <pattern>   : skip any IP addresses before <pattern> in the command's output"],
+    ["cmd",          "=s", "-cmd <command>        : deprecated, use 'cmdv4' or 'cmdv6'"],
+    ["cmd-skip",     "=s", "-cmd-skip <pattern>   : deprecated, filter in program wrapper script"],
+    ["cmdv4",        "=s", "-cmdv4 <command>      : obtain IPv4 address from the output of <command>"],
+    ["cmdv6",        "=s", "-cmdv6 <command>      : obtain IPv6 address from the output of <command>"],
     "",
     ["login",        "=s", "-login <user>         : log in to the dynamic DNS service as <user>"],
     ["password",     "=s", "-password <secret>    : log in to the dynamic DNS service with password <secret>"],
@@ -812,19 +896,22 @@ my @opt = (
     ["ssl",          "!",  "-{no}ssl              : do updates over encrypted SSL connection"],
     ["ssl_ca_dir",   "=s", "-ssl_ca_dir <dir>     : look in <dir> for certificates of trusted certificate authorities (default: auto-detect)"],
     ["ssl_ca_file",  "=s", "-ssl_ca_file <file>   : look at <file> for certificates of trusted certificate authorities (default: auto-detect)"],
+    ["fw-ssl-validate","!", "-{no}fw-ssl-validate  : Validate SSL certificate when retrieving IP address from firewall"],
+    ["web-ssl-validate","!","-{no}web-ssl-validate : Validate SSL certificate when retrieving IP address from web"],
+    ["curl",         "!",  "-{no}curl             : use curl for network connections"],
     ["retry",        "!",  "-{no}retry            : retry failed updates"],
     ["force",        "!",  "-{no}force            : force an update even if the update may be unnecessary"],
     ["timeout",      "=i", "-timeout <max>        : when fetching a URL, wait at most <max> seconds for a response"],
     ["syslog",       "!",  "-{no}syslog           : log messages to syslog"],
     ["facility",     "=s", "-facility <type>      : log messages to syslog to facility <type>"],
     ["priority",     "=s", "-priority <pri>       : log messages to syslog with priority <pri>"],
+    ["max-warn",     "=i", "-max-warn <max>       : log at most <max> warning messages for undefined IP address"],
     ["mail",         "=s", "-mail <address>       : e-mail messages to <address>"],
     ["mail-failure", "=s", "-mail-failure <addr>  : e-mail messages for failed updates to <addr>"],
     ["exec",         "!",  "-{no}exec             : do {not} execute; just show what would be done"],
     ["debug",        "!",  "-{no}debug            : print {no} debugging information"],
     ["verbose",      "!",  "-{no}verbose          : print {no} verbose information"],
     ["quiet",        "!",  "-{no}quiet            : print {no} messages for unnecessary updates"],
-    ["ipv6",         "!",  "-{no}ipv6             : use ipv6"],
     ["help",         "",   "-help                 : display this message and exit"],
     ["postscript",   "",   "-postscript           : script to run after updating ddclient, has new IP as param"],
     ["query",        "!",  "-{no}query            : print {no} ip addresses and exit"],
@@ -900,6 +987,10 @@ sub main {
 
         fatal("invalid argument '-use %s'; possible values are:\n%s", $opt{'use'}, join("\n", ip_strategies_usage()))
             unless exists $ip_strategies{lc opt('use')};
+        if (defined($opt{'usev6'})) {
+            usage("invalid argument '-usev6 %s'; possible values are:\n%s", $opt{'usev6'}, join("\n",ipv6_strategies_usage()))
+                unless exists $ipv6_strategies{lc opt('usev6')};
+        }
 
         $daemon = opt('daemon');
 
@@ -961,9 +1052,11 @@ sub runpostscript {
 sub update_nics {
     my %examined = ();
     my %iplist   = ();
+    my %ipv4list = ();
+    my %ipv6list = ();
 
     foreach my $s (sort keys %services) {
-        my (@hosts, %ips) = ();
+        my (@hosts, %ipsv4, %ipsv6) = ();
         my $updateable = $services{$s}{'updateable'};
         my $update     = $services{$s}{'update'};
 
@@ -971,33 +1064,103 @@ sub update_nics {
             next if $config{$h}{'protocol'} ne lc($s);
             $examined{$h} = 1;
             # we only do this once per 'use' and argument combination
-            my $use = opt('use', $h);
-            my $arg_ip = opt('ip', $h) // '';
-            my $arg_fw = opt('fw', $h) // '';
-            my $arg_if = opt('if', $h) // '';
-            my $arg_web = opt('web', $h) // '';
-            my $arg_cmd = opt('cmd', $h) // '';
-            my $ip = "";
-            if (exists $iplist{$use}{$arg_ip}{$arg_fw}{$arg_if}{$arg_web}{$arg_cmd}) {
-                $ip = $iplist{$use}{$arg_ip}{$arg_fw}{$arg_if}{$arg_web}{$arg_cmd};
-            } else {
-                $ip = get_ip($use, $h);
-                if (!defined($ip)) {
-                    warning("unable to determine IP address")
-                        if !$daemon || opt('verbose');
-                    next;
+            my $use       = opt('use',   $h) // 'disabled';
+            my $usev4     = opt('usev4', $h) // 'disabled';
+            my $usev6     = opt('usev6', $h) // 'disabled';
+            $use          = 'disabled' if ($use eq 'no'); # backward compatibility
+            $usev6        = 'disabled' if ($usev6 eq 'no'); # backward compatibility
+            my $arg_ip    = opt('ip',    $h) // '';
+            my $arg_ipv4  = opt('ipv4',  $h) // '';
+            my $arg_ipv6  = opt('ipv6',  $h) // '';
+            my $arg_fw    = opt('fw',    $h) // '';
+            my $arg_fwv4  = opt('fwv4',  $h) // '';
+            my $arg_fwv6  = opt('fwv6',  $h) // '';
+            my $arg_if    = opt('if',    $h) // '';
+            my $arg_ifv4  = opt('ifv4',  $h) // '';
+            my $arg_ifv6  = opt('ifv6',  $h) // '';
+            my $arg_web   = opt('web',   $h) // '';
+            my $arg_webv4 = opt('webv4', $h) // '';
+            my $arg_webv6 = opt('webv6', $h) // '';
+            my $arg_cmd   = opt('cmd',   $h) // '';
+            my $arg_cmdv4 = opt('cmdv4', $h) // '';
+            my $arg_cmdv6 = opt('cmdv6', $h) // '';
+            my $ip = undef;
+            my $ipv4 = undef;
+            my $ipv6 = undef;
+
+            if ($use ne 'disabled') {
+                if (exists $iplist{$use}{$arg_ip}{$arg_fw}{$arg_if}{$arg_web}{$arg_cmd}) {
+                    # If we have already done a get_ip() for this, don't do it again.
+                    $ip = $iplist{$use}{$arg_ip}{$arg_fw}{$arg_if}{$arg_web}{$arg_cmd};
+                } else {
+                    # Else need to find the IP address...
+                    $ip = get_ip($use, $h);
+                    if (is_ipv4($ip) || is_ipv6($ip)) {
+                         # And if it is valid, remember it...
+                        $iplist{$use}{$arg_ip}{$arg_fw}{$arg_if}{$arg_web}{$arg_cmd} = $ip;
+                    } else {
+                        warning("%s: unable to determine IP address with strategy use=%s", $h, $use)
+                            if !$daemon || opt('verbose');
+                    }
                 }
-                $iplist{$use}{$arg_ip}{$arg_fw}{$arg_if}{$arg_web}{$arg_cmd} = $ip;
+                # And remember it as the IP address we want to send to the DNS service.
+                $config{$h}{'wantip'} = $ip;
             }
-            $config{$h}{'wantip'} = $ip;
+
+            if ($usev4 ne 'disabled') {
+                if (exists $ipv4list{$usev4}{$arg_ipv4}{$arg_fwv4}{$arg_ifv4}{$arg_webv4}{$arg_cmdv4}) {
+                    # If we have already done a get_ipv4() for this, don't do it again.
+                    $ipv4 = $ipv4list{$usev4}{$arg_ipv4}{$arg_fwv4}{$arg_ifv4}{$arg_webv4}{$arg_cmdv4};
+                } else {
+                    # Else need to find the IPv4 address...
+                    $ipv4 = get_ipv4($usev4, $h);
+                    if (is_ipv4($ipv4)) {
+                         # And if it is valid, remember it...
+                        $ipv4list{$usev4}{$arg_ipv4}{$arg_fwv4}{$arg_ifv4}{$arg_webv4}{$arg_cmdv4} = $ipv4;
+                    } else {
+                        warning("%s: unable to determine IPv4 address with strategy usev4=%s", $h, $usev4)
+                            if !$daemon || opt('verbose');
+                    }
+                }
+                # And remember it as the IPv4 address we want to send to the DNS service.
+                $config{$h}{'wantipv4'} = $ipv4;
+            }
+
+            if ($usev6 ne 'disabled') {
+                if (exists $ipv6list{$usev6}{$arg_ipv6}{$arg_fwv6}{$arg_ifv6}{$arg_webv6}{$arg_cmdv6}) {
+                    # If we have already done a get_ipv6() for this, don't do it again.
+                    $ipv6 = $ipv6list{$usev6}{$arg_ipv6}{$arg_fwv6}{$arg_ifv6}{$arg_webv6}{$arg_cmdv6};
+                } else {
+                    # Else need to find the IPv6 address...
+                    $ipv6 = get_ipv6($usev6, $h);
+                    if (is_ipv6($ipv6)) {
+                        # And if it is valid, remember it...
+                        $ipv6list{$usev6}{$arg_ipv6}{$arg_fwv6}{$arg_ifv6}{$arg_webv6}{$arg_cmdv6} = $ipv6;
+                    } else {
+                        warning("%s: unable to determine IPv6 address with strategy usev6=%s", $h, $usev6)
+                            if !$daemon || opt('verbose');
+                    }
+                }
+                # And remember it as the IP address we want to send to the DNS service.
+                $config{$h}{'wantipv6'} = $ipv6;
+            }
+
+            # DNS service update functions should only have to handle 'wantipv4' and 'wantipv6'
+            $config{$h}{'wantipv4'} = $ipv4 = $ip if (!$ipv4 && is_ipv4($ip));
+            $config{$h}{'wantipv6'} = $ipv6 = $ip if (!$ipv6 && is_ipv6($ip));
+            # But we will set 'wantip' to the IPv4 so old functions continue to work until we update them all
+            $config{$h}{'wantip'}   = $ipv4       if (!$ip && $ipv4);
+
             next if !nic_updateable($h, $updateable);
             push @hosts, $h;
-            $ips{$ip} = $h;
+
+            $ipsv4{$ipv4} = $h if ($ipv4);
+            $ipsv6{$ipv6} = $h if ($ipv6);
         }
         if (@hosts) {
             $0 = sprintf("%s - updating %s", $program, join(',', @hosts));
             &$update(@hosts);
-            runpostscript(join ' ', keys %ips);
+            runpostscript(join ' ', keys %ipsv4, keys %ipsv6);
         }
     }
     foreach my $h (sort keys %config) {
@@ -1045,8 +1208,7 @@ sub write_cache {
     ## merge the updated host entries into the cache.
     foreach my $h (keys %config) {
         if (!exists $cache{$h} || $config{$h}{'update'}) {
-            map { $cache{$h}{$_} = $config{$h}{$_} } @{$config{$h}{'cacheable'}};
-
+	        map { defined($config{$h}{$_}) ? ($cache{$h}{$_} = $config{$h}{$_}) : () } @{$config{$h}{'cacheable'}};
         } else {
             map { $cache{$h}{$_} = $config{$h}{$_} } qw(atime wtime status);
         }
@@ -1334,10 +1496,22 @@ sub init_config {
     $opt{'quiet'} = 0 if opt('verbose');
 
     ## infer the IP strategy if possible
-    if (!defined($opt{'use'})) {
-        $opt{'use'} = 'web' if defined($opt{'web'});
-        $opt{'use'} = 'if'  if defined($opt{'if'});
-        $opt{'use'} = 'ip'  if defined($opt{'ip'});
+    if (!$opt{'use'}) {
+        $opt{'use'} = 'web' if ($opt{'web'});
+        $opt{'use'} = 'if'  if ($opt{'if'});
+        $opt{'use'} = 'ip'  if ($opt{'ip'});
+    }
+    ## infer the IPv4 strategy if possible
+    if (!$opt{'usev4'}) {
+        $opt{'usev4'} = 'webv4' if ($opt{'webv4'});
+        $opt{'usev4'} = 'ifv4'  if ($opt{'ifv4'});
+        $opt{'usev4'} = 'ipv4'  if ($opt{'ipv4'});
+    }
+    ## infer the IPv6 strategy if possible
+    if (!$opt{'usev6'}) {
+        $opt{'usev6'} = 'webv6' if ($opt{'webv6'});
+        $opt{'usev6'} = 'ifv6'  if ($opt{'ifv6'});
+        $opt{'usev6'} = 'ipv6'  if ($opt{'ipv6'});
     }
 
     ## sanity check
@@ -1525,6 +1699,7 @@ sub process_args {
 sub test_possible_ip {
     local $opt{'debug'} = 0;
 
+    printf "----- Test_possible_ip with 'get_ip' -----\n";
     printf "use=ip, ip=%s address is %s\n", opt('ip'), get_ip('ip') // 'NOT FOUND'
         if defined opt('ip');
 
@@ -1568,6 +1743,75 @@ sub test_possible_ip {
         local $opt{'use'} = 'cmd';
         printf "use=cmd, cmd=%s address is %s\n", opt('cmd'), get_ip('cmd') // 'NOT FOUND';
     }
+
+    # Now force IPv4
+    printf "----- Test_possible_ip with 'get_ipv4' ------\n";
+    printf "use=ipv4, ipv4=%s address is %s\n", opt('ipv4'), get_ipv4('ipv4') // 'NOT FOUND'
+        if defined opt('ipv4');
+
+    {
+        # Note: The `ip` command adds a `@eth0` suffix to the names of VLAN
+        # interfaces. That `@eth0` suffix is NOT part of the interface name.
+        my @ifs = map({ /^[^\s:]*:\s*([^\s:@]+)/ ? $1 : () }
+                      `command -v ip >/dev/null && ip -o link show`);
+        @ifs = map({ /^([a-zA-Z].*?)(?::?\s.*)?$/ ? $1 : () }
+                   `command -v ifconfig >/dev/null && ifconfig -a`) if $? || !@ifs;
+        @ifs = () if $?;
+        warning("failed to get list of interfaces") if !@ifs;
+        foreach my $if (@ifs) {
+            local $opt{'ifv4'} = $if;
+            printf "use=ifv4, ifv4=%s address is %s\n", opt('ifv4'), get_ipv4('ifv4') // 'NOT FOUND';
+        }
+    }
+    {
+        local $opt{'usev4'} = 'webv4';
+        foreach my $web (sort keys %builtinweb) {
+            local $opt{'webv4'} = $web;
+            printf "use=webv4, webv4=$web address is %s\n", get_ipv4('webv4') // 'NOT FOUND'
+                if ($web !~ "6")  ## Don't bother if web site only supports IPv6;
+        }
+        printf "use=webv4, webv4=%s address is %s\n", opt('webv4'), get_ipv4('webv4') // 'NOT FOUND'
+            if ! exists $builtinweb{opt('webv4')};
+    }
+    if (opt('cmdv4')) {
+        local $opt{'usev4'} = 'cmdv4';
+        printf "use=cmdv4, cmdv4=%s address is %s\n", opt('cmdv4'), get_ipv4('cmdv4') // 'NOT FOUND';
+    }
+
+    # Now force IPv6
+    printf "----- Test_possible_ip with 'get_ipv6' -----\n";
+    printf "use=ipv6, ipv6=%s address is %s\n", opt('ipv6'), get_ipv6('ipv6') // 'NOT FOUND'
+        if defined opt('ipv6');
+
+    {
+        # Note: The `ip` command adds a `@eth0` suffix to the names of VLAN
+        # interfaces. That `@eth0` suffix is NOT part of the interface name.
+        my @ifs = map({ /^[^\s:]*:\s*([^\s:@]+)/ ? $1 : () }
+                      `command -v ip >/dev/null && ip -o link show`);
+        @ifs = map({ /^([a-zA-Z].*?)(?::?\s.*)?$/ ? $1 : () }
+                   `command -v ifconfig >/dev/null && ifconfig -a`) if $? || !@ifs;
+        @ifs = () if $?;
+        warning("failed to get list of interfaces") if !@ifs;
+        foreach my $if (@ifs) {
+            local $opt{'ifv6'} = $if;
+            printf "use=ifv6, ifv6=%s address is %s\n", opt('ifv6'), get_ipv6('ifv6') // 'NOT FOUND';
+        }
+    }
+    {
+        local $opt{'usev6'} = 'webv6';
+        foreach my $web (sort keys %builtinweb) {
+            local $opt{'webv6'} = $web;
+            printf "use=webv6, webv6=$web address is %s\n", get_ipv6('webv6') // 'NOT FOUND'
+                if ($web !~ "4");  ## Don't bother if web site only supports IPv4
+        }
+        printf "use=webv6, webv6=%s address is %s\n", opt('webv6'), get_ipv6('webv6') // 'NOT FOUND'
+            if ! exists $builtinweb{opt('webv6')};
+    }
+    if (opt('cmdv6')) {
+        local $opt{'usev6'} = 'cmdv6';
+        printf "use=cmdv6, cmdv6=%s address is %s\n", opt('cmdv6'), get_ipv6('cmdv6') // 'NOT FOUND';
+    }
+
     exit 0 unless opt('debug');
 }
 ######################################################################
@@ -1940,6 +2184,14 @@ sub check_value {
         $value = lc $value;
         return undef if !exists $ip_strategies{$value};
 
+    } elsif ($type eq T_USEV4) {
+        $value = lc $value;
+        return undef if ! exists $ipv4_strategies{$value};
+
+    } elsif ($type eq T_USEV6) {
+        $value = lc $value;
+        return undef if ! exists $ipv6_strategies{$value};
+
     } elsif ($type eq T_FILE) {
         return undef if $value eq "";
 
@@ -1954,6 +2206,13 @@ sub check_value {
 
     } elsif ($type eq T_IP) {
         return undef if !is_ipv4($value) && !is_ipv6($value);
+
+    } elsif ($type eq T_IPV4) {
+        return undef if !is_ipv4($value);
+
+    } elsif ($type eq T_IPV6) {
+        return undef if !is_ipv6($value);
+
     }
     return $value;
 }
@@ -2042,10 +2301,15 @@ EOM
     }
     import JSON::PP (qw/decode_json encode_json/);
 }
+
 ######################################################################
 ## geturl
 ######################################################################
 sub geturl {
+    return opt('curl') ? fetch_via_curl(@_) : fetch_via_socket_io(@_);
+}
+
+sub fetch_via_socket_io {
     my %params = @_;
     my $proxy = $params{proxy};
     my $url = $params{url};
@@ -2098,7 +2362,7 @@ sub geturl {
     } else {
         $request .= "https://$server" if defined($proxy);
     }
-    $request .= "/$url HTTP/1.0\n";
+    $request .= "/$url HTTP/1.1\n";
     $request .= "Host: $server\n";
 
     if (defined($login) || defined($password)) {
@@ -2133,6 +2397,9 @@ sub geturl {
         $socket_class = 'IO::Socket::SSL';
         $socket_args{SSL_ca_file} = opt('ssl_ca_file') if defined(opt('ssl_ca_file'));
         $socket_args{SSL_ca_path} = opt('ssl_ca_dir') if defined(opt('ssl_ca_dir'));
+        $socket_args{SSL_verify_mode} = ($params{ssl_validate} // 1)
+                                        ? IO::Socket::SSL->SSL_VERIFY_PEER
+                                        : IO::Socket::SSL->SSL_VERIFY_NONE;
     } elsif ($globals{'ipv6'} || $ipversion eq '6') {
         load_ipv6_support;
         $socket_class = 'IO::Socket::INET6';
@@ -2213,11 +2480,232 @@ sub geturl {
     return $reply;
 }
 
+######################################################################
+## curl_cmd() function to execute system curl command
+######################################################################
+sub curl_cmd {
+    my @params = @_;
+    my $tmpfile;
+    my $tfh;
+    my $system_curl = quotemeta(subst_var('@CURL@', 'curl'));
+    my %curl_codes = (  ## Subset of error codes from https://curl.haxx.se/docs/manpage.html
+         2 => "Failed to initialize. (Most likely a bug in ddclient, please open issue at https://github.com/ddclient/ddclient)",
+         3 => "URL malformed. The syntax was not correct",
+         5 => "Couldn't resolve proxy. The given proxy host could not be resolved.",
+         6 => "Couldn't resolve host. The given remote host was not resolved.",
+         7 => "Failed to connect to host.",
+        22 => "HTTP page not retrieved. The requested url was not found or returned another error.",
+        28 => "Operation timeout. The specified time-out period was reached according to the conditions.",
+        35 => "SSL connect error. The SSL handshaking failed.",
+        47 => "Too many redirects. When following redirects, curl hit the maximum amount.",
+        52 => "The server didn't reply anything, which here is considered an error.",
+        51 => "The peer's SSL certificate or SSH MD5 fingerprint was not OK.",
+        58 => "Problem with the local certificate.",
+        60 => "Peer certificate cannot be authenticated with known CA certificates.",
+        67 => "The user name, password, or similar was not accepted and curl failed to log in.",
+        77 => "Problem with reading the SSL CA cert (path? access rights?).",
+        78 => "The resource referenced in the URL does not exist.",
+       127 => "You requested network access with curl but $system_curl was not found",
+    );
+
+    debug("CURL: %s", $system_curl);
+    fatal("curl not found") if ($system_curl eq '');
+    return '' if (scalar(@params) == 0); ## no parameters provided
+
+    # Hard code to /tmp rather than use system TMPDIR to protect from malicious
+    # shell instructions in TMPDIR environment variable.  All systems should have /tmp.
+    $tfh = File::Temp->new(DIR => '/tmp',
+                           TEMPLATE => 'ddclient_XXXXXXXXXX');
+    $tmpfile = $tfh->filename;
+
+    debug("CURL Tempfile: %s", $tmpfile);
+    {
+        local $\ = "\n";  ## Terminate the file,
+        local $, = "\n";  ## and each parameter, with a newline.
+        print($tfh @params);
+    }
+    close($tfh);
+    my $reply = qx{ $system_curl --config $tmpfile 2>/dev/null; };
+    if ((my $rc = $?>>8) != 0) {
+        warning("CURL error (%d) %s", $rc, $curl_codes{$rc} // "Unknown return code. Check $system_curl is installed and its manpage.");
+    }
+    return $reply;
+}
+
+######################################################################
+## escape_curl_param() makes sure any special characters within a
+## curl parameter is properly escaped.
+######################################################################
+sub escape_curl_param {
+    my $str = shift // '';
+
+    return '' if ($str eq '');
+    $str =~ s/\\/\\\\/g;## Escape backslashes
+    $str =~ s/"/\\"/g;  ## Escape double-quotes
+    $str =~ s/\n/\\n/g; ## Escape newline
+    $str =~ s/\r/\\r/g; ## Escape carrage return
+    $str =~ s/\t/\\t/g; ## Escape tabs
+    $str =~ s/\v/\\v/g; ## Escape vertical whitespace
+    return $str;
+}
+
+######################################################################
+## fetch_via_curl() is used for geturl() when global curl option set
+######################################################################
+sub fetch_via_curl {
+    my %params = @_;
+    my $proxy = $params{proxy};
+    my $url = $params{url};
+    my $login = $params{login};
+    my $password = $params{password};
+    my $ipversion = ($params{ipversion}) ? int($params{ipversion}) : 0;
+    my $headers = $params{headers} // '';
+    my $method = $params{method} // 'GET';
+    my $data = $params{data} // '';
+
+    my $reply;
+    my $server;
+    my $use_ssl = 0;
+    my $force_ssl = 0;
+    my $protocol;
+    my $timeout  = opt('timeout');
+    my @curlopt = ();
+    my @header_lines = ();
+
+    ## canonify proxy and url
+    $force_ssl = 1 if ($url =~ /^https:/);
+    $proxy  =~ s%^https?://%%i if defined($proxy);
+    $url    =~ s%^https?://%%i;
+    $server = $url;
+    $server =~ s%[?/].*%%;
+    $url    =~ s%^[^?/]*/?%%;
+
+    $use_ssl = 1 if ($force_ssl || ($globals{'ssl'} && !($params{ignore_ssl_option} // 0)));
+
+    $protocol = ($use_ssl ? "https" : "http");
+
+    debug("proxy    = %s", $proxy // '<undefined>');
+    debug("protocol = %s", $protocol);
+    debug("server   = %s", $server);
+    (my $_url = $url) =~ s%\?.*%?<redacted>%; #redact possible credentials
+    debug("url      = %s", $_url);
+    debug("ip ver   = %s", $ipversion);
+
+    if (!opt('exec')) {
+        debug("skipped network connection");
+        verbose("SENDING:", "%s", "${server}/${url}");
+    } else {
+        my $curl_loaded = eval { require WWW::Curl::Easy };
+        if ($curl_loaded) {
+            # System has the WWW::Curl::Easy module so use that
+            import WWW::Curl::Easy;
+            my $curl = WWW::Curl::Easy->new;
+
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_HEADER, 1);   ## Include HTTP response for compatibility
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_SSL_VERIFYPEER, ($params{ssl_validate} // 1) ? 1 : 0 );
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_SSL_VERIFYHOST, ($params{ssl_validate} // 1) ? 1 : 0 );
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_CAINFO, opt('ssl_ca_file')) if defined(opt('ssl_ca_file'));
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_CAPATH, opt('ssl_ca_dir')) if defined(opt('ssl_ca_dir'));
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_IPRESOLVE,
+                                            ($ipversion == 4) ? WWW::Curl::Easy->CURL_IPRESOLVE_V4 : 
+                                            ($ipversion == 6) ? WWW::Curl::Easy->CURL_IPRESOLVE_V6 :
+                                                                WWW::Curl::Easy->CURL_IPRESOLVE_WHATEVER);
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_USERAGENT, "${program}/${version}");
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_CONNECTTIMEOUT, $timeout);
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_TIMEOUT, $timeout);
+
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_POST, 1) if ($method eq 'POST');
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_PUT, 1) if ($method eq 'PUT');
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_CUSTOMREQUEST, $method) if ($method ne 'GET'); ## for PATCH
+
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_USERPWD, "${login}:${password}") if (defined($login) && defined($password));
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_PROXY, "${protocol}://${proxy}") if defined($proxy);
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_URL, "${protocol}://${server}/${url}");
+
+            # Add header lines if any was provided
+            if ($headers) {
+                @header_lines = split('\n', $headers);
+                $curl->setopt(WWW::Curl::Easy->CURLOPT_HTTPHEADER, \@header_lines);
+            }
+            # Add in the data if any was provided (for POST/PATCH)
+            if (my $datalen = length($data)) {
+                $curl->setopt(WWW::Curl::Easy->CURLOPT_POSTFIELDS, ${data});
+                $curl->setopt(WWW::Curl::Easy->CURLOPT_POSTFIELDSIZE, $datalen);
+            }
+            $curl->setopt(WWW::Curl::Easy->CURLOPT_WRITEDATA,\$reply);
+
+            # don't include ${url} as that might expose login credentials
+            $0 = sprintf("%s - WWW::Curl::Easy sending to %s", $program, "${protocol}://${server}");
+            verbose("SENDING:", "WWW::Curl::Easy to %s", "${protocol}://${server}");
+            verbose("SENDING:", "%s", $headers) if ($headers);
+            verbose("SENDING:", "%s", $data) if ($data);
+
+            my $rc = $curl->perform;
+
+            if ($rc != 0) {
+                warning("CURL error (%d) %s", $rc, $curl->strerror($rc));
+                debug($curl->errbuf);
+            }
+        } else {
+            # System does not have the WWW::Curl::Easy module so attempt with system Curl command
+            push(@curlopt, "silent");
+            push(@curlopt, "include");  ## Include HTTP response for compatibility
+            push(@curlopt, "insecure") if ($use_ssl && !($params{ssl_validate} // 1));
+            push(@curlopt, "cacert=\"".escape_curl_param(opt('ssl_ca_file')).'"') if defined(opt('ssl_ca_file'));
+            push(@curlopt, "capath=\"".escape_curl_param(opt('ssl_ca_dir')).'"') if defined(opt('ssl_ca_dir'));
+            push(@curlopt, "ipv4") if ($ipversion == 4);
+            push(@curlopt, "ipv6") if ($ipversion == 6);
+            push(@curlopt, "user-agent=\"".escape_curl_param("${program}/${version}").'"');
+            push(@curlopt, "connect-timeout=$timeout");
+            push(@curlopt, "max-time=$timeout");
+            push(@curlopt, "request=$method");
+            push(@curlopt, "user=\"".escape_curl_param("${login}:${password}").'"') if (defined($login) && defined($password));
+            push(@curlopt, "proxy=\"".escape_curl_param("${protocol}://${proxy}").'"') if defined($proxy);
+            push(@curlopt, "url=\"".escape_curl_param("${protocol}://${server}/${url}").'"');
+
+            # Each header line is added individually
+            @header_lines = split('\n', $headers);
+            $_ = "header=\"".escape_curl_param($_).'"' foreach (@header_lines);
+            push(@curlopt, @header_lines);
+
+            # Add in the data if any was provided (for POST/PATCH)
+            push(@curlopt, "data=\"".escape_curl_param(${data}).'"') if ($data);
+
+            # don't include ${url} as that might expose login credentials
+            $0 = sprintf("%s - Curl system cmd sending to %s", $program, "${protocol}://${server}");
+            verbose("SENDING:", "Curl system cmd to %s", "${protocol}://${server}");
+            verbose("SENDING:", "%s", $_) foreach (@curlopt);
+
+            $reply = curl_cmd(@curlopt);
+        }
+        verbose("RECEIVE:", "%s", $reply // "<undefined>");
+        if (!$reply) {
+            # don't include ${url} as that might expose login credentials
+            warning("curl cannot connect to %s://%s using IPv%s",${protocol},${server},$ipversion);
+        }
+    }
+
+    ## during testing simulate reading the URL
+    if (opt('test')) {
+        my $filename = "$server/$url";
+        $filename =~ s|/|%2F|g;
+        if (opt('exec')) {
+            $reply = save_file("$savedir/$filename", $reply, 'unique');
+        } else {
+            $reply = load_file("$savedir/$filename");
+        }
+    }
+
+    $reply =~ s/\r//g if defined $reply;
+    return $reply;
+}
+
 ######################################################################
 ## get_ip
 ######################################################################
 sub get_ip {
     my $use = lc shift;
+    $use    = 'disabled' if ($use eq 'no'); # backward compatibility
     my $h   = shift;
     my ($ip, $arg, $reply, $url, $skip) = (undef, opt($use, $h), '');
     $arg = '' unless $arg;
@@ -2225,15 +2713,13 @@ sub get_ip {
     if ($use eq 'ip') {
         $ip  = opt('ip', $h);
         if (!is_ipv4($ip) && !is_ipv6($ip)) {
-            warning("'%s' is not a valid IPv4 or IPv6 address", $ip);
+            warning("'%s' is not a valid IPv4 or IPv6 address", $ip // '');
             $ip = undef;
         }
         $arg = 'ip';
 
     } elsif ($use eq 'if') {
-        $reply = `command -v ip >/dev/null && ip address show dev $arg`;
-        $reply = `command -v ifconfig >/dev/null && ifconfig $arg` if $?;
-        $reply = '' if $?;
+        $ip = get_ip_from_interface($arg);
 
     } elsif ($use eq 'cmd') {
         if ($arg) {
@@ -2253,7 +2739,11 @@ sub get_ip {
         $arg = $url;
 
         if ($url) {
-            $reply = geturl(proxy => opt('proxy', $h), url => $url) // '';
+            $reply = geturl(
+                proxy => opt('proxy', $h),
+                url => $url,
+                ssl_validate => opt('web-ssl-validate', $h),
+            ) // '';
         }
 
     } elsif (($use eq 'cisco')) {
@@ -2275,6 +2765,7 @@ sub get_ip {
             login => opt('fw-login', $h),
             password => opt('fw-password', $h),
             ignore_ssl_option => 1,
+            ssl_validate => opt('fw-ssl-validate', $h),
         ) // '';
         $arg = $url;
 
@@ -2297,9 +2788,14 @@ sub get_ip {
             login => opt('fw-login', $h),
             password => opt('fw-password', $h),
             ignore_ssl_option => 1,
+            ssl_validate => opt('fw-ssl-validate', $h),
         ) // '';
         $arg = $url;
 
+    } elsif ($use eq 'disabled') {
+        ## This is a no-op... Do not get an IP address for this host/service
+        $reply = '';
+
     } else {
         $url = opt('fw', $h) // '';
         $skip = opt('fw-skip', $h) // '';
@@ -2316,6 +2812,7 @@ sub get_ip {
                 login => opt('fw-login', $h),
                 password => opt('fw-password', $h),
                 ignore_ssl_option => 1,
+                ssl_validate => opt('fw-ssl-validate', $h),
             ) // '';
         }
     }
@@ -2336,7 +2833,6 @@ sub get_ip {
     return $ip;
 }
 
-
 ######################################################################
 ## Regex to find IPv4 address. Accepts embedded leading zeros.
 ######################################################################
@@ -2427,6 +2923,10 @@ sub extract_ipv6 {
     return $ip;
 }
 
+######################################################################
+## Regex that matches an IPv6 address that is probably globally routable.
+## Accepts embedded leading zeros.
+######################################################################
 my $regex_ipv6_global = qr{
     (?!  # Is not one of the following addresses:
         0{0,4}:             # ::/16 is assumed to never contain globaly routable addresses
@@ -2459,10 +2959,417 @@ sub extract_ipv6_global {
     return $ip;
 }
 
+######################################################################
+## Regex that matches an IPv6 address that is unique local (ULA).
+## Accepts embedded leading zeros.
+######################################################################
+my $regex_ipv6_ula = qr{
+    (?=  # Address starts with
+      f[cd][0-9a-f]{2}:     # fc00::/7 RFC4193 ULA
+    )
+    $regex_ipv6             # And is a valid IPv6 address
+}xi;
+
+######################################################################
+## get_default_interface finds the default network interface based on
+## the IP routing table on the system.  We validate that the interface
+## found is likely to have global routing (e.g. is not LOOPBACK).
+## Returns undef if no global scope interface can be found for IP version.
+######################################################################
+sub get_default_interface {
+    my $ipver = int(shift // 4);    ## Defaults to IPv4 if not specified
+    my $ipstr = ($ipver == 6) ? 'inet6' : 'inet';
+    my $reply = shift // '';  ## Pass in data for unit testing purposes only
+    my $cmd = "test";
+
+    return undef if (($ipver != 4) && ($ipver != 6));
+
+    if (!$reply) { ## skip if test data passed in.
+        ## Best option is the ip command from iproute2 package
+        $cmd = "ip -$ipver -o route list match default"; $reply = qx{ $cmd 2>/dev/null };
+        ## Fallback is the netstat command. This is only option on MacOS.
+        if ($?) { $cmd = "netstat -rn -$ipver";     $reply = qx{ $cmd 2>/dev/null }; } # Linux, FreeBSD
+        if ($?) { $cmd = "netstat -rn -f $ipstr";   $reply = qx{ $cmd 2>/dev/null }; } # MacOS
+        if ($?) { $cmd = "netstat -rn";             $reply = qx{ $cmd 2>/dev/null }; } # Busybox
+        if ($?) { $cmd = "missing ip or netstat command";
+            failed("Unable to obtain default route information -- %s", $cmd)
+        }
+    }
+    debug("Reply from '%s' :\n------\n%s------", $cmd, $reply);
+
+    # Check we have IPv6 address in case we got routing table from non-specific cmd above
+    return undef if (($ipver == 6) && !extract_ipv6($reply));
+    # Filter down to just the default interfaces
+    my @list = split(/\n/, $reply);
+    @list = grep(/^default|^(?:0\.){3}0|^::\/0/, @list); # Select 'default' or '0.0.0.0' or '::/0'
+    return undef if (scalar(@list) == 0);
+    debug("Default routes found for IPv%s :\n%s", $ipver, join("\n",@list));
+
+    # now check each interface to make sure it is global (not loopback).
+    foreach my $line (@list) {
+        ## Interface will be after "dev" or the last word in the line. Must accept blank spaces
+        ## at the end.  Interface name may not have any whitespace or forward slash.
+        $line =~ /\bdev\b\s*\K[^\s\/]+|\b[^\s\/]+(?=[\s\/]*$)/;
+        my $interface = $&;
+        ## If test data was passed in skip following tests
+        if ($cmd ne "test") {
+            ## We do not want the loopback interface or anything interface without global scope
+            $cmd = "ip -$ipver -o addr show dev $interface scope global"; $reply = qx{$cmd 2>/dev/null};
+            if ($?) { $cmd = "ifconfig $interface";                       $reply = qx{$cmd 2>/dev/null}; }
+            if ($?) { $cmd = "missing ip or ifconfig command";
+                failed("Unable to obtain information for '%s' -- %s", $interface, $cmd);
+            }
+            debug("Reply from '%s' :\n------\n%s------", $cmd, $reply);
+        }
+        ## Has global scope, is not LOOPBACK
+        return($interface) if (($reply) && ($reply !~ /\bLOOPBACK\b/));
+    }
+    return undef;
+}
+
+######################################################################
+## get_ip_from_interface() finds an IPv4 or IPv6 address from a network
+## interface. Defaults to IPv4 unless '6' passed as 2nd parameter.
+######################################################################
+sub get_ip_from_interface {
+    my $interface = shift // "default";
+    my $ipver = int(shift // 4);    ## Defaults to IPv4 if not specified
+    my $scope = lc(shift // "gua"); ## "gua" or "ula"
+    my $reply = shift // '';  ## Pass in data for unit testing purposes only
+    my $MacOS = shift // 0;   ## For testing can set to 1 if input data is MacOS/FreeBSD format
+    my $count = 0;
+    my $cmd = "test";
+
+    if (($ipver != 4) && ($ipver != 6)) {
+        warning("get_ip_from_interface() invalid IP version: %s", $ipver);
+        return undef;
+    }
+
+    if ((lc($interface) eq "default") && (!$reply)) { ## skip if test data passed in.
+        $interface = get_default_interface($ipver);
+        return undef if !defined($interface);
+    }
+
+    if ($ipver == 4) {
+        if (!$reply) { ## skip if test data passed in.
+            ## Try ip first, then ifconfig.
+            $cmd = "ip -4 -o addr show dev $interface scope global"; $reply = qx{$cmd 2>/dev/null};
+            if ($?) { $cmd = "ifconfig $interface";                  $reply = qx{$cmd 2>/dev/null}; }
+            if ($?) { $cmd = "missing ip or ifconfig command";
+                failed("Unable to obtain information for '%s' -- %s", $interface, $cmd);
+            }
+        }
+        debug("Reply from '%s' :\n------\n%s------", $cmd, $reply);
+
+        ## IPv4 is simple, we just need to find the first IPv4 address returned in the list.
+        my @reply = split(/\n/, $reply);
+        @reply = grep(/\binet\b/, @reply);  # Select only IPv4 entries
+        return extract_ipv4($reply[0]);
+    }
+
+    ## From this point on we only looking for IPv6 address.
+    if (($scope ne "gua") && ($scope ne "ula")) {
+        warning("get_ip_from_interface() invalid IPv6 scope: %s, using type GUA", $scope);
+        $scope = "gua";
+    }
+
+    $cmd = "test data";
+    if (!$reply) { ## skip if test data passed in.
+        ## Try ip first, then ifconfig with -L for MacOS/FreeBSD then finally ifconfig for everything else
+        $cmd = "ip -6 -o addr show dev $interface scope global"; $reply = qx{$cmd 2>/dev/null};   # Linux
+        if ($?) { $cmd = "ifconfig -L $interface"; $MacOS = 1;   $reply = qx{$cmd 2>/dev/null}; } # MacOS/FreeBSD
+        if ($?) { $cmd = "ifconfig $interface";                  $reply = qx{$cmd 2>/dev/null}; } # Anything without iproute2 or -L
+        if ($?) { $cmd = "missing ip or ifconfig command";
+            failed("Unable to obtain information for '%s' -- %s", $interface, $cmd);
+        }
+    }
+    debug("Reply from '%s' :\n------\n%s------", $cmd, $reply);
+
+    ## IPv6 is more complex than IPv4.  Start by filtering on only "inet6" addresses
+    ## Then remove deprecated or temporary addresses and finally seleect on global or local addresses 
+    my @reply = split(/\n/, $reply);
+    @reply = grep(/\binet6\b/, @reply);                             # Select only IPv6 entries
+    @reply = grep(!/\bdeprecated\b|\btemporary\b/, @reply);         # Remove deprecated and temporary
+    @reply = ($scope eq "gua") ? grep(/$regex_ipv6_global/, @reply) # Select only global addresses
+                               : grep(/$regex_ipv6_ula/, @reply);   #   or only ULA addresses
+    debug("Raw IPv6 after filtering for %s addresses %s: (%s)\r\n%s", uc($scope), $interface, scalar(@reply), join("\n", @reply));
+
+    ## If we filter down to zero or one result then we are done...
+    return undef if (($count = scalar(@reply)) == 0);
+    return extract_ipv6($reply[0]) if ($count == 1);
+
+    ## If there are more than one we need to select the "best".
+    ## First choice would be a static address.
+    my @static = ($MacOS == 1) ? grep(!/^.*\bvltime\b.*$/i, @reply)              # MacOS/FreeBSD, no 'vltime'
+                               : grep(/^.*\bvalid_lft.\bforever\b.*$/i, @reply); # Everything else 'forever' life
+    $count = scalar(@static);
+    debug("Possible Static IP addresses %s: (%s)\r\n%s", $interface, $count, join("\n", @static));
+
+    ## If only one result then we are done.  If there are more than one static addresses
+    ## then we will replace our original list with the list of statics and sort on them.
+    ## If zero static addresses we fall through with our original list.
+    return extract_ipv6($static[0]) if ($count == 1);
+    @reply = @static if ($count > 1);
+
+    ## Sort what we have by the prefix length, IP address "length" and finally valid life.
+    my @sorted = sort {
+        ## We give preference to IP addressess with the longest prefix... so we prefer a /128 over a /64
+        ## this is a decimal (\d+) either after the word "prefixlen" or after a forward slash.
+        (($b =~ /(?:\bprefixlen\b\s*|\/)(\d+)/i)[0] // 0) <=> (($a =~ /(?:\bprefixlen\b\s*|\/)(\d+)/i)[0] // 0)
+
+        ## If there are multiple the same then we prefer "shorter" IP addresses in the
+        ## theory that a shorter address is more likely assigned by DHCPv6 than SLAAC.
+        ## E.g. 2001:db8:4341:0781::8214/64 is preferable to 2001:db8:4341:0781:34a6:c329:c52e:8ba6/64
+        ## So we count the number () of groups of [0-9a-f] blocks in the IP address.
+     || (()= (extract_ipv6($a) // '') =~ /[0-9A-F]+/gi) <=> (()= (extract_ipv6($b) // '') =~ /[0-9A-F]+/gi)
+
+        ## Finally we check remaining valid lifetime and prefer longer remaining life.
+        ## This is a desimal (\d+) after the word "valid_lft" or "vltime". Only available
+        ## from iproute2 or MacOS/FreeBSD version of ifconfig (-L parameter).
+     || (($b =~ /(?:\bvalid_lft\b\s*|\bvltime\b\s*)(\d+)/i)[0] // 0) <=> (($a =~ /(?:\bvalid_lft\b\s*|\bvltime\b\s*)(\d+)/i)[0] // 0)
+    } @reply;
+    debug("Sorted list of IP addresss for %s: (%s)\r\n%s", $interface, scalar(@sorted), join("\n", @sorted));
+
+    ## Whatever sorted to the top is the best choice for IPv6 address
+    return extract_ipv6($sorted[0]);
+}
+
+######################################################################
+## get_ipv4
+######################################################################
+sub get_ipv4 {
+    my $usev4 = lc(shift);  ## Method to obtain IP address
+    my $h     = shift;      ## Host/service making the request
+
+    my $ipv4  = undef;      ## Found IPv4 address
+    my $reply = '';         ## Text returned from various methods
+    my $url   = '';         ## URL of website or firewall
+    my $skip  = '';         ## Regex of pattern to skip before looking for IP
+    my $arg   = opt($usev4, $h) // '';  ## Value assigned to the "usev4" method
+
+    if ($usev4 eq 'ipv4') {
+        ## Static IPv4 address is provided in "ipv4=<address>"
+        $ipv4  = $arg;
+        if (!is_ipv4($ipv4)) {
+            warning("'%s' is not a valid IPv4",$ipv4 // '');
+            $ipv4 = undef;
+        }
+        $arg = 'ipv4';  # For debug message at end of function
+
+    } elsif ($usev4 eq 'ifv4') {
+        ## Obtain IPv4 address from interface mamed in "ifv4=<if>"
+        warning("'if-skip' is deprecated and does nothing for IPv4") if (opt('verbose') && opt('if-skip', $h));
+        $ipv4 = get_ip_from_interface($arg,4);
+
+    } elsif ($usev4 eq 'cmdv4') {
+        ## Obtain IPv4 address by executing the command in "cmdv4=<command>"
+        warning("'cmd-skip' is deprecated and does nothing for IPv4") if (opt('verbose') && opt('cmd-skip', $h));
+        if ($arg) {
+            my $sys_cmd = quotemeta($arg);
+            $reply = qx{$sys_cmd};
+            $reply = '' if $?;
+        }
+
+    } elsif ($usev4 eq 'webv4') {
+        ## Obtain IPv4 address by accessing website at url in "webv4=<url>"
+        $url = $arg;
+        $skip = opt('webv4-skip', $h) // '';
+        if (exists $builtinweb{$url}) {
+            $skip = $builtinweb{$url}->{'skip'} unless $skip;
+            $url  = $builtinweb{$url}->{'url'};
+            $arg  = $url;
+        }
+        if ($url) {
+            $reply = geturl( proxy => opt('proxy', $h),
+                url => $url,
+                ipversion => 4, # when using a URL to find IPv4 address we should force use of IPv4
+                ssl_validate => opt('ssl-validate', $h),
+            ) // '';
+        }
+
+    } elsif ($usev4 eq 'cisco' || $usev4 eq 'cisco-asa') {
+        # Stuff added to support Cisco router ip http or ASA https daemon
+        # User fw-login should only have level 1 access to prevent
+        # password theft.  This is pretty harmless.
+        warning("'if' does nothing for IPv4. Use 'ifv4'") if (opt('if', $h));
+        warning("'fw' does nothing for IPv4. Use 'fwv4'") if (opt('fw', $h));
+        warning("'fw-skip' does nothing for IPv4. Use 'fwv4-skip'") if (opt('fw-skip', $h));
+        my $queryif = opt('ifv4', $h) // opt('if', $h);
+        $skip = opt('fwv4-skip', $h) // opt('fw-skip', $h) // '';
+        # Convert slashes to protected value "\/"
+        $queryif =~ s%\/%\\\/%g;
+        # Protect special HTML characters (like '?')
+        $queryif =~ s/([\?&= ])/sprintf("%%%02x", ord($1))/ge;
+        if ($usev4 eq 'cisco') {
+            $url = "http://" . (opt('fwv4', $h) // opt('fw', $h)) . "/level/1/exec/show/ip/interface/brief/${queryif}/CR";
+        } else {
+            $url = "https://" . (opt('fwv4', $h) // opt('fw', $h))  . "/exec/show%20interface%20${queryif}";
+        }
+        $arg = $url;
+        $reply = geturl(
+            url => $url,
+            login => opt('fw-login', $h),
+            password => opt('fw-password', $h),
+            ipversion => 4, # when using a URL to find IPv4 address we should force use of IPv4
+            ignore_ssl_option => 1,
+            ssl_validate => opt('ssl-validate', $h),
+        ) // '';
+
+    } elsif ($usev4 eq 'disabled') {
+        ## This is a no-op... Do not get an IPv4 address for this host/service
+        $reply = '';
+
+    } else {
+        warning("'fw' does nothing for IPv4. Use 'fwv4'") if (opt('fw', $h));
+        warning("'fw-skip' does nothing for IPv4. Use 'fwv4-skip'") if (opt('fw-skip', $h));
+        $url  = opt('fwv4', $h) // opt('fw', $h) // '';
+        $skip = opt('fwv4-skip', $h) // opt('fw-skip', $h) // '';
+
+        if (exists $builtinfw{$usev4}) {
+            $skip = $builtinfw{$usev4}->{'skip'} unless $skip;
+            $url  = "http://${url}" . $builtinfw{$usev4}->{'url'} unless $url =~ /\//;
+        }
+        $arg = $url;
+        if ($url) {
+            $reply = geturl(
+                url => $url,
+                login => opt('fw-login', $h),
+                password => opt('fw-password', $h),
+                ipversion => 4, # when using a URL to find IPv4 address we should force use of IPv4
+                ignore_ssl_option => 1,
+                ssl_validate => opt('ssl-validate', $h),
+            ) // '';
+        }
+    }
+
+    ## Set to loopback address if no text set yet
+    $reply = '0.0.0.0' if !defined($reply);
+    if (($skip // '') ne '') {
+        $skip  =~ s/ /\\s/is;
+        $reply =~ s/^.*?${skip}//is;
+    }
+    ## If $ipv4 not set yet look for IPv4 address in the $reply text
+    $ipv4 //= extract_ipv4($reply);
+    ## Return undef for loopback address unless statically assigned by "ipv4=0.0.0.0"
+    $ipv4 = undef if (($usev4 ne 'ipv4') && (($ipv4 // '') eq '0.0.0.0'));
+    debug("get_ipv4: using (%s, %s) reports %s", $usev4, $arg, $ipv4 // "<undefined>");
+    return $ipv4;
+}
+
+######################################################################
+## get_ipv6
+######################################################################
+sub get_ipv6 {
+    my $usev6 = lc(shift);  ## Method to obtain IP address
+    $usev6    = 'disabled' if ($usev6 eq 'no'); # backward compatibility
+    my $h     = shift;      ## Host/service making the request
+
+    my $ipv6  = undef;      ## Found IPv6 address
+    my $reply = '';         ## Text returned from various methods
+    my $url   = '';         ## URL of website or firewall
+    my $skip  = '';         ## Regex of pattern to skip before looking for IP
+    my $arg   = opt($usev6, $h) // '';  ## Value assigned to the "usev6" method
+
+    if ($usev6 eq 'ipv6' || $usev6 eq 'ip') {
+        ## Static IPv6 address is provided in "ipv6=<address>"
+        if ($usev6 eq 'ip') {
+            warning("'usev6=ip' is deprecated. Use 'usev6=ipv6'");
+            $usev6 = 'ipv6';
+            ## If there is a value for ipv6= use that, else use value for ip=
+            $arg = opt($usev6, $h) // $arg;
+        }
+        $ipv6 = $arg;
+        if (!is_ipv6($ipv6)) {
+            warning("'%s' is not a valid IPv6",$ipv6 // '');
+            $ipv6 = undef;
+        }
+        $arg = 'ipv6';  # For debug message at end of function
+
+    } elsif ($usev6 eq 'ifv6' || $usev6 eq 'if' ) {
+        ## Obtain IPv6 address from interface mamed in "ifv6=<if>"
+        if ($usev6 eq 'if') {
+            warning("'usev6=if' is deprecated. Use 'usev6=ifv6'");
+            $usev6 = 'ifv6';
+            ## If there is a value for ifv6= use that, else use value for if=
+            $arg = opt($usev6, $h) // $arg;
+        }
+        warning("'if-skip' is deprecated and does nothing for IPv6") if (opt('verbose') && opt('if-skip', $h));
+        $ipv6 = get_ip_from_interface($arg,6);
+
+    }  elsif ($usev6 eq 'cmdv6' || $usev6 eq 'cmd') {
+        ## Obtain IPv6 address by executing the command in "cmdv6=<command>"
+        if ($usev6 eq 'cmd') {
+            warning("'usev6=cmd' is deprecated. Use 'usev6=cmdv6'");
+            $usev6 = 'cmdv6';
+            ## If there is a value for cmdv6= use that, else use value for cmd=
+            $arg = opt($usev6, $h) // $arg;
+        }
+        warning("'cmd-skip' is deprecated and does nothing for IPv6") if (opt('verbose') && opt('cmd-skip', $h));
+        if ($arg) {
+            my $sys_cmd = quotemeta($arg);
+            $reply = qx{$sys_cmd};
+            $reply = '' if $?;
+        }
+
+    } elsif ($usev6 eq 'webv6' || $usev6 eq 'web') {
+        ## Obtain IPv6 address by accessing website at url in "webv6=<url>"
+        if ($usev6 eq 'web') {
+            warning("'usev6=web' is deprecated. Use 'usev6=webv6'");
+            $usev6 = 'webv6';
+            ## If there is a value for webv6= use that, else use value for web=
+            $arg = opt($usev6, $h) // $arg;
+        }
+        warning("'web-skip' does nothing for IPv6. Use 'webv6-skip'") if (opt('web-skip', $h));
+        $url = $arg;
+        $skip = opt('webv6-skip', $h) // '';
+        if (exists $builtinweb{$url}) {
+            $skip = $builtinweb{$url}->{'skip'} unless $skip;
+            $url  = $builtinweb{$url}->{'url'};
+            $arg  = $url;
+        }
+        if ($url) {
+            $reply = geturl(
+                proxy => opt('proxy'),
+                url => $url,
+                ipversion => 6, # when using a URL to find IPv6 address we should force use of IPv6
+                ssl_validate => opt('ssl-validate', $h),
+            ) // '';
+        }
+
+    } elsif ($usev6 eq 'cisco' || $usev6 eq 'cisco-asa') {
+        warning("'usev6=cisco' and 'usev6=cisco-asa' are not implemented and do nothing");
+        $reply = '';
+
+    } elsif ($usev6 eq 'disabled') {
+        ## This is a no-op... Do not get an IPv6 address for this host/service
+        warning("'usev6=no' is deprecated. Use 'usev6=disabled'") if ($usev6 eq 'no');
+        $reply = '';
+
+    } else {
+        warning("'usev6=%s' is not implemented and does nothing", $usev6);
+        $reply = '';
+
+    }
+
+    ## Set to loopback address if no text set yet
+    $reply = '::' if !defined($reply);
+    if (($skip // '') ne '') {
+        $skip  =~ s/ /\\s/is;
+        $reply =~ s/^.*?${skip}//is;
+    }
+    ## If $ipv6 not set yet look for IPv6 address in the $reply text
+    $ipv6 //= extract_ipv6($reply);
+    ## Return undef for loopback address unless statically assigned by "ipv6=::"
+    $ipv6 = undef if (($usev6 ne 'ipv6') && (($ipv6 // '') eq '::'));
+    debug("get_ipv6: using (%s, %s) reports %s", $usev6, $arg, $ipv6 // "<undefined>");
+    return $ipv6;
+}
+
 ######################################################################
 ## group_hosts_by
 ######################################################################
 sub group_hosts_by {
+##TODO - Update for wantipv4 and wantipv6
     my ($hosts, $attributes) = @_;
     my %attrs = (map({ ($_ => 1) } @$attributes), 'wantip' => 1);
     my @attrs = sort(keys(%attrs));
@@ -2570,12 +3477,35 @@ EoEXAMPLE
 }
 ######################################################################
 ## nic_updateable
+## Returns true if we can go ahead and update the IP address at server
 ######################################################################
 sub nic_updateable {
     my $host   = shift;
     my $sub    = shift;
     my $update = 0;
     my $ip     = $config{$host}{'wantip'};
+    my $ipv4   = $config{$host}{'wantipv4'};
+    my $ipv6   = $config{$host}{'wantipv6'};
+    my $use    = opt('use',   $host) // 'disabled';
+    my $usev4  = opt('usev4', $host) // 'disabled';
+    my $usev6  = opt('usev6', $host) // 'disabled';
+    $use       = 'disabled' if ($use eq 'no');   # backward compatibility
+    $usev6     = 'disabled' if ($usev6 eq 'no'); # backward compatibility
+
+    # If we have a valid IP address and we have previously warned that it was invalid.
+    # reset the warning count back to zero.
+    if (($use ne 'disabled') && $ip && $warned_ip{$host}) {
+        $warned_ip{$host} = 0;
+        warning("IP address for %s valid: %s. Reset warning count", $host, $ip);
+    }
+    if (($usev4 ne 'disabled') && $ipv4 && $warned_ipv4{$host}) {
+        $warned_ipv4{$host} = 0;
+        warning("IPv4 address for %s valid: %s. Reset warning count", $host, $ipv4);
+    }
+    if (($usev6 ne 'disabled') && $ipv6 && $warned_ipv6{$host}) {
+        $warned_ipv6{$host} = 0;
+        warning("IPv6 address for %s valid: %s. Reset warning count", $host, $ipv6);
+    }
 
     if ($config{$host}{'login'} eq '') {
         warning("null login name specified for host %s.", $host);
@@ -2607,7 +3537,9 @@ sub nic_updateable {
         );
         $update = 1;
 
-    } elsif (!exists($cache{$host}{'ip'}) || $cache{$host}{'ip'} ne $ip) {
+    } elsif ( ($use ne 'disabled')
+           && ((!exists($cache{$host}{'ip'})) || ("$cache{$host}{'ip'}" ne "$ip"))) {
+        ## Check whether to update IP address for the "use" method"
         if (($cache{$host}{'status'} eq 'good') &&
             !interval_expired($host, 'mtime', 'min-interval')) {
 
@@ -2622,17 +3554,117 @@ sub nic_updateable {
 
             $cache{$host}{'warned-min-interval'} = $now;
 
-        } elsif (($cache{$host}{'status'} ne 'good') && !interval_expired($host, 'atime', 'min-error-interval')) {
+        } elsif (($cache{$host}{'status'} ne 'good') &&
+            !interval_expired($host, 'atime', 'min-error-interval')) {
 
-            warning("skipping update of %s from %s to %s.\nlast updated %s but last attempt on %s failed.\nWait at least %s between update attempts.",
+            if ( opt('verbose')
+                 || ( ! $cache{$host}{'warned-min-error-interval'}
+                     && (($warned_ip{$host} // 0) < $inv_ip_warn_count)) ) {
+
+                warning("skipping update of %s from %s to %s.\nlast updated %s but last attempt on %s failed.\nWait at least %s between update attempts.",
+                        $host,
+                        ($cache{$host}{'ip'}    ? $cache{$host}{'ip'}                : '<nothing>'),
+                        $ip,
+                        ($cache{$host}{'mtime'} ? prettytime($cache{$host}{'mtime'}) : '<never>'),
+                        ($cache{$host}{'atime'} ? prettytime($cache{$host}{'atime'}) : '<never>'),
+                        prettyinterval($config{$host}{'min-error-interval'})
+                );
+                if (!$ip && !opt('verbose')) {
+                    $warned_ip{$host} = ($warned_ip{$host} // 0) + 1;
+                    warning("IP address for %s undefined. Warned %s times, suppressing further warnings", $host, $inv_ip_warn_count)
+                        if ($warned_ip{$host} >= $inv_ip_warn_count);
+                }
+            }
+
+            $cache{$host}{'warned-min-error-interval'} = $now;
+
+        } else {
+            $update = 1;
+        }
+
+    } elsif ( ($usev4 ne 'disabled')
+           && ((!exists($cache{$host}{'ipv4'})) || ("$cache{$host}{'ipv4'}" ne "$ipv4"))) {
+        ## Check whether to update IPv4 address for the "usev4" method"
+        if (($cache{$host}{'status-ipv4'} eq 'good') &&
+            !interval_expired($host, 'mtime', 'min-interval')) {
+
+            warning("skipping update of %s from %s to %s.\nlast updated %s.\nWait at least %s between update attempts.",
                     $host,
-                    ($cache{$host}{'ip'}    ? $cache{$host}{'ip'}                : '<nothing>'),
-                    $ip,
+                    ($cache{$host}{'ipv4'}  ? $cache{$host}{'ipv4'}              : '<nothing>'),
+                    $ipv4,
                     ($cache{$host}{'mtime'} ? prettytime($cache{$host}{'mtime'}) : '<never>'),
-                    ($cache{$host}{'atime'} ? prettytime($cache{$host}{'atime'}) : '<never>'),
-                    prettyinterval($config{$host}{'min-error-interval'})
+                    prettyinterval($config{$host}{'min-interval'})
             )
-                if opt('verbose') || !($cache{$host}{'warned-min-error-interval'} // 0);
+                if opt('verbose') || !($cache{$host}{'warned-min-interval'} // 0);
+
+            $cache{$host}{'warned-min-interval'} = $now;
+
+        } elsif (($cache{$host}{'status-ipv4'} ne 'good') &&
+            !interval_expired($host, 'atime', 'min-error-interval')) {
+
+            if ( opt('verbose')
+                 || ( ! $cache{$host}{'warned-min-error-interval'}
+                     && (($warned_ipv4{$host} // 0) < $inv_ip_warn_count)) ) {
+
+                warning("skipping update of %s from %s to %s.\nlast updated %s but last attempt on %s failed.\nWait at least %s between update attempts.",
+                        $host,
+                        ($cache{$host}{'ipv4'}  ? $cache{$host}{'ipv4'}              : '<nothing>'),
+                        $ipv4,
+                        ($cache{$host}{'mtime'} ? prettytime($cache{$host}{'mtime'}) : '<never>'),
+                        ($cache{$host}{'atime'} ? prettytime($cache{$host}{'atime'}) : '<never>'),
+                        prettyinterval($config{$host}{'min-error-interval'})
+                );
+                if (!$ipv4 && !opt('verbose')) {
+                    $warned_ipv4{$host} = ($warned_ipv4{$host} // 0) + 1;
+                    warning("IPv4 address for %s undefined. Warned %s times, suppressing further warnings", $host, $inv_ip_warn_count)
+                        if ($warned_ipv4{$host} >= $inv_ip_warn_count);
+                }
+            }
+
+            $cache{$host}{'warned-min-error-interval'} = $now;
+
+        } else {
+            $update = 1;
+        }
+
+    } elsif ( ($usev6 ne 'disabled')
+           && ((!exists($cache{$host}{'ipv6'})) || ("$cache{$host}{'ipv6'}" ne "$ipv6"))) {
+        ## Check whether to update IPv6 address for the "usev6" method"
+        if (($cache{$host}{'status-ipv6'} eq 'good') &&
+            !interval_expired($host, 'mtime', 'min-interval')) {
+
+            warning("skipping update of %s from %s to %s.\nlast updated %s.\nWait at least %s between update attempts.",
+                    $host,
+                    ($cache{$host}{'ipv6'}  ? $cache{$host}{'ipv6'}              : '<nothing>'),
+                    $ipv6,
+                    ($cache{$host}{'mtime'} ? prettytime($cache{$host}{'mtime'}) : '<never>'),
+                    prettyinterval($config{$host}{'min-interval'})
+            )
+                if opt('verbose') || !($cache{$host}{'warned-min-interval'} // 0);
+
+            $cache{$host}{'warned-min-interval'} = $now;
+
+        } elsif (($cache{$host}{'status-ipv6'} ne 'good') &&
+            !interval_expired($host, 'atime', 'min-error-interval')) {
+
+            if ( opt('verbose')
+                 || ( ! $cache{$host}{'warned-min-error-interval'}
+                     && (($warned_ipv6{$host} // 0) < $inv_ip_warn_count)) ) {
+
+                warning("skipping update of %s from %s to %s.\nlast updated %s but last attempt on %s failed.\nWait at least %s between update attempts.",
+                        $host,
+                        ($cache{$host}{'ipv6'}  ? $cache{$host}{'ipv6'}              : '<nothing>'),
+                        $ipv6,
+                        ($cache{$host}{'mtime'} ? prettytime($cache{$host}{'mtime'}) : '<never>'),
+                        ($cache{$host}{'atime'} ? prettytime($cache{$host}{'atime'}) : '<never>'),
+                        prettyinterval($config{$host}{'min-error-interval'})
+                );
+                if (!$ipv6 && !opt('verbose')) {
+                    $warned_ipv6{$host} = ($warned_ipv6{$host} // 0) + 1;
+                    warning("IPv6 address for %s undefined. Warned %s times, suppressing further warnings", $host, $inv_ip_warn_count)
+                        if ($warned_ipv6{$host} >= $inv_ip_warn_count);
+                }
+            }
 
             $cache{$host}{'warned-min-error-interval'} = $now;
 
@@ -2654,13 +3686,27 @@ sub nic_updateable {
         $update = 1;
 
     } else {
-        success("%s: skipped: IP address was already set to %s.", $host, $ip)
-            if opt('verbose');
+        if (opt('verbose')) {
+            if ($use ne 'disabled') {
+                success("%s: skipped: IP address was already set to %s.", $host, $ip);
+            }
+            if ($usev4 ne 'disabled') {
+                success("%s: skipped: IPv4 address was already set to %s.", $host, $ipv6);
+            }
+            if ($usev6 ne 'disabled') {
+                success("%s: skipped: IPv6 address was already set to %s.", $host, $ipv6);
+            }
+        }
     }
+
     $config{$host}{'status'} = $cache{$host}{'status'} // '';
+    $config{$host}{'status-ipv4'} = $cache{$host}{'status-ipv4'} // '';
+    $config{$host}{'status-ipv6'} = $cache{$host}{'status-ipv6'} // '';
     $config{$host}{'update'} = $update;
     if ($update) {
         $config{$host}{'status'}                    = 'noconnect';
+        $config{$host}{'status-ipv4'}               = 'noconnect';
+        $config{$host}{'status-ipv6'}               = 'noconnect';
         $config{$host}{'atime'}                     = $now;
         $config{$host}{'wtime'}                     = 0;
         $config{$host}{'warned-min-interval'}       = 0;
@@ -2680,7 +3726,7 @@ sub header_ok {
     my ($host, $line) = @_;
     my $ok = 0;
 
-    if ($line =~ m%^s*HTTP/1.*\s+(\d+)%i) {
+    if ($line =~ m%^s*HTTP/.*\s+(\d+)%i) {
         my $result = $1;
 
         if ($result =~ m/^2\d\d$/) {
@@ -3919,12 +4965,14 @@ EoEXAMPLE
 ##   hostname2.example.com|5.6.7.8|http://example/update/url3
 ##   hostname2.example.com|9.10.11.12|http://example/update/url4
 ##   hostname3.example.com|cafe::f00d|http://example/update/url5
+##   hostname4.example.com|NULL|http://example/update/url6
 ##
 ## The record's columns are separated by '|'. The first is the hostname, the second is the current
 ## address, and the third is the record-specific update URL. There can be multiple records for the
-## same host, and they can even have the same address type. Any record can be updated to hold
-## either type of address (e.g., if given an IPv6 address the record will automatically become an
-## AAAA record).
+## same host, and they can even have the same address type. To update an IP address the record
+## must already exist of the type we want to update... We will not change a record type from
+## an IPv4 to IPv6 or viz versa.  Records may exist with a NULL address which we will allow to be
+## updated with an IPv4 address, not an IPv6.
 ##
 ## The second step is to visit the appropriate record's update URL with
 ## ?address=<ipv4-or-ipv6-address> appended. "Updated" in the result means success, "fail" means
@@ -3940,7 +4988,10 @@ sub nic_freedns_update {
     my $url_tmpl = "http://$config{$_[0]}{'server'}/api/?action=getdyndns&v=2&sha=<credentials>";
     my $creds = sha1_hex("$config{$_[0]}{'login'}|$config{$_[0]}{'password'}");
     (my $url = $url_tmpl) =~ s/<credentials>/$creds/;
-    my $reply = geturl(proxy => opt('proxy'), url => $url);
+
+    my $reply = geturl(proxy => opt('proxy'),
+                       url => $url
+                      );
     my $record_list_error = '';
     if ($reply && header_ok($_[0], $reply)) {
         $reply =~ s/^.*?\n\n//s;  # Strip the headers.
@@ -3949,7 +5000,8 @@ sub nic_freedns_update {
             next if ($#rec < 2);
             my $recs = is_ipv6($rec[1]) ? \%recs_ipv6 : \%recs_ipv4;
             $recs->{$rec[0]} = \@rec;
-            debug("host: %s, current address: %s, update URL: %s", @rec);
+            # Update URL contains credentials that don't require login to use, so best to hide.
+            debug("host: %s, current address: %s, update URL: <redacted>", $rec[0], $rec[1]);
         }
         if (keys(%recs_ipv4) + keys(%recs_ipv6) == 0) {
             chomp($reply);
@@ -3960,54 +5012,61 @@ sub nic_freedns_update {
     }
 
     foreach my $h (@_) {
-        if (!$h) { next }
-        my $ip = delete $config{$h}{'wantip'};
-
-        info("%s: setting IP address to %s", $h, $ip);
+        next if (!$h);
+        my $ipv4 = delete $config{$h}{'wantipv4'};
+        my $ipv6 = delete $config{$h}{'wantipv6'};
 
         if ($record_list_error ne '') {
-            $config{$h}{'status'} = 'failed';
+            $config{$h}{'status-ipv4'} = 'failed' if ($ipv4);
+            $config{$h}{'status-ipv6'} = 'failed' if ($ipv6);
             failed("updating %s: %s", $h, $record_list_error);
             next;
         }
-        # If there is a record with matching type then update it, otherwise let
-        # freedns convert the record to the desired type.
-        my $rec = is_ipv6($ip)
-            ? ($recs_ipv6{$h} // $recs_ipv4{$h})
-            : ($recs_ipv4{$h} // $recs_ipv6{$h});
-        if (!defined($rec)) {
-            $config{$h}{'status'} = 'failed';
-            failed("updating %s: host record does not exist", $h);
-            next;
-        }
 
-        if ($ip eq $rec->[1]) {
-            $config{$h}{'ip'}     = $ip;
-            $config{$h}{'mtime'}  = $now;
-            $config{$h}{'status'} = 'good';
-            success("update not necessary %s: good: IP address already set to %s", $h, $ip)
-                if (!$daemon || opt('verbose'));
-        } else {
-            my $url = $rec->[2] . "&address=" . $ip;
-            debug("Update: %s", $url);
-            my $reply = geturl(proxy => opt('proxy'), url => $url);
-            if (!defined($reply) || !$reply || !header_ok($h, $reply)) {
-                $config{$h}{'status'} = 'failed';
-                failed("updating %s: Could not connect to %s.", $h, $url);
+        # IPv4 and IPv6 handling are similar enough to do in a loop...
+        foreach my $ip ($ipv4, $ipv6) {
+            next if (!$ip);
+            my $ipv  = ($ip eq ($ipv6 // '')) ? '6' : '4';
+            my $type = ($ip eq ($ipv6 // '')) ? 'AAAA' : 'A';
+            my $rec  = ($ip eq ($ipv6 // '')) ? $recs_ipv6{$h}
+                                              : $recs_ipv4{$h};
+            if (!$rec) {
+                failed("updating %s: Cannot set IPv$ipv to %s No '$type' record at FreeDNS", $h, $ip);
                 next;
             }
 
-            $reply =~ s/^.*?\n\n//s;  # Strip the headers.
-            if ($reply =~ /Updated.*$h.*to.*$ip/) {
-                $config{$h}{'ip'}     = $ip;
-                $config{$h}{'mtime'}  = $now;
-                $config{$h}{'status'} = 'good';
-                success("updating %s: good: IP address set to %s", $h, $ip);
+            info("updating %s: setting IP address to %s", $h, $ip);
+            $config{$h}{"status-ipv$ipv"} = 'failed';
+
+            if ($ip eq $rec->[1]) {
+                $config{$h}{"ipv$ipv"} = $ip;
+                $config{$h}{'mtime'} = $now;
+                $config{$h}{"status-ipv$ipv"} = 'good';
+                success("updating %s: update not necessary, '$type' record already set to %s", $h, $ip)
+                    if (!$daemon || opt('verbose'));
             } else {
-                $config{$h}{'status'} = 'failed';
-                warning("SENT: %s", $url) unless opt('verbose');
-                warning("REPLIED: %s", $reply);
-                failed("updating %s: Invalid reply.", $h);
+                my $url = $rec->[2] . "&address=" . $ip;
+                ($url_tmpl = $url) =~ s/\?.*\&/?<redacted>&/; # redact unique update token
+                debug("updating: %s", $url_tmpl);
+
+                my $reply = geturl(proxy => opt('proxy'),
+                                   url => $url
+                                  );
+                if ($reply && header_ok($h, $reply)) {
+                    $reply =~ s/^.*?\n\n//s;  # Strip the headers.
+                    if ($reply =~ /Updated.*$h.*to.*$ip/) {
+                        $config{$h}{"ipv$ipv"} = $ip;
+                        $config{$h}{'mtime'} = $now;
+                        $config{$h}{"status-ipv$ipv"} = 'good';
+                        success("updating %s: good: IPv$ipv address set to %s", $h, $ip);
+                    } else {
+                        warning("SENT: %s", $url_tmpl) unless opt('verbose');
+                        warning("REPLIED: %s", $reply);
+                        failed("updating %s: Invalid reply.", $h);
+                    }
+                } else {
+                    failed("updating %s: Could not connect to %s.", $h, $url_tmpl);
+                }
             }
         }
     }
@@ -4319,6 +5378,7 @@ Example ${program}.conf file entries:
   ## single host update using an API token
   protocol=cloudflare,                                         \\
   zone=dns.zone,                                               \\
+  login=token,                                                 \\
   password=cloudflare-api-token                                \\
   myhost.com
 
@@ -4344,7 +5404,6 @@ sub nic_cloudflare_update {
         my @hosts = @{$groups{$sig}};
         my $hosts = join(',', @hosts);
         my $key   = $hosts[0];
-        my $ip    = $config{$key}{'wantip'};
 
         my $headers = "Content-Type: application/json\n";
         if ($config{$key}{'login'} eq 'token') {
@@ -4357,102 +5416,104 @@ sub nic_cloudflare_update {
         # FQDNs
         for my $domain (@hosts) {
             (my $hostname = $domain) =~ s/\.$config{$key}{zone}$//;
-            delete $config{$domain}{'wantip'};
+            my $ipv4  = delete $config{$domain}{'wantipv4'};
+            my $ipv6  = delete $config{$domain}{'wantipv6'};
 
-            info("setting IP address to %s for %s", $ip, $domain);
-            verbose("UPDATE:", "updating %s", $domain);
+            info("getting Cloudflare Zone ID for %s", $domain);
 
             # Get zone ID
             my $url = "https://$config{$key}{'server'}/zones?";
-            $url .= "name=".$config{$key}{'zone'};
+            $url .= "name=" . $config{$key}{'zone'};
 
-            my $reply = geturl(proxy => opt('proxy'), url => $url, headers => $headers);
-            unless ($reply) {
+            my $reply = geturl(proxy => opt('proxy'),
+                               url => $url,
+                               headers => $headers
+                              );
+            unless ($reply && header_ok($domain, $reply)) {
                 failed("updating %s: Could not connect to %s.", $domain, $config{$key}{'server'});
                 next;
             }
-            next if !header_ok($domain, $reply);
 
             # Strip header
             $reply =~ s/^.*?\n\n//s;
-            my $response = eval { decode_json($reply) };
-            if (!defined $response || !defined $response->{result}) {
-                failed("invalid json or result.");
+            my $response = eval {decode_json($reply)};
+            unless ($response && $response->{result}) {
+                failed("updating %s: invalid json or result.", $domain);
                 next;
             }
 
             # Pull the ID out of the json, messy
-            my ($zone_id) = map { $_->{name} eq $config{$key}{'zone'} ? $_->{id} : () } @{$response->{result}};
+            my ($zone_id) = map {$_->{name} eq $config{$key}{'zone'} ? $_->{id} : ()} @{$response->{result}};
             unless ($zone_id) {
                 failed("updating %s: No zone ID found.", $config{$key}{'zone'});
                 next;
             }
-            info("zone ID is %s", $zone_id);
+            info("Zone ID is %s", $zone_id);
 
-            # Get DNS record ID
-            $url = "https://$config{$key}{'server'}/zones/$zone_id/dns_records?";
-            if (is_ipv6($ip)) {
-                $url .= "type=AAAA&name=$domain";
-            } else {
-                $url .= "type=A&name=$domain";
+
+            # IPv4 and IPv6 handling are similar enough to do in a loop...
+            foreach my $ip ($ipv4, $ipv6) {
+                next if (!$ip);
+                my $ipv  = ($ip eq ($ipv6 // '')) ? '6' : '4';
+                my $type = ($ip eq ($ipv6 // '')) ? 'AAAA' : 'A';
+
+                info("updating %s: setting IPv$ipv address to %s", $domain, $ip);
+                $config{$domain}{"status-ipv$ipv"} = 'failed';
+
+                # Get DNS 'A' or 'AAAA' record ID
+                $url = "https://$config{$key}{'server'}/zones/$zone_id/dns_records?";
+                $url .= "type=$type&name=$domain";
+                $reply = geturl(proxy => opt('proxy'),
+                                url => $url,
+                                headers => $headers
+                               );
+                unless ($reply && header_ok($domain, $reply)) {
+                    failed("updating %s: Could not connect to %s.", $domain, $config{$key}{'server'});
+                    next;
+                }
+                # Strip header
+                $reply =~ s/^.*?\n\n//s;
+                $response = eval {decode_json($reply)};
+                unless ($response && $response->{result}) {
+                    failed("updating %s: invalid json or result.", $domain);
+                    next;
+                }
+                # Pull the ID out of the json, messy
+                my ($dns_rec_id) = map {$_->{name} eq $domain ? $_->{id} : ()} @{$response->{result}};
+                unless($dns_rec_id) {
+                    failed("updating %s: Cannot set IPv$ipv to %s No '$type' record at Cloudflare", $domain, $ip);
+                    next;
+                }
+                debug("updating %s: DNS '$type' record ID: $dns_rec_id", $domain);
+                # Set domain
+                $url = "https://$config{$key}{'server'}/zones/$zone_id/dns_records/$dns_rec_id";
+                my $data = "{\"content\":\"$ip\"}";
+                $reply = geturl(proxy => opt('proxy'),
+                                url => $url,
+                                headers => $headers,
+                                method => "PATCH",
+                                data => $data
+                               );
+                unless ($reply && header_ok($domain, $reply)) {
+                    failed("updating %s: Could not connect to %s.", $domain, $config{$domain}{'server'});
+                    next;
+                }
+                # Strip header
+                $reply =~ s/^.*?\n\n//s;
+                $response = eval {decode_json($reply)};
+                if ($response && $response->{result}) {
+                    success("updating %s: IPv$ipv address set to %s", $domain, $ip);
+                    $config{$domain}{"ipv$ipv"} = $ip;
+                    $config{$domain}{'mtime'} = $now;
+                    $config{$domain}{"status-ipv$ipv"} = 'good';
+                } else {
+                    failed("updating %s: invalid json or result.", $domain);
+                }
             }
-
-            $reply = geturl(proxy => opt('proxy'), url => $url, headers => $headers);
-            unless ($reply) {
-                failed("updating %s: Could not connect to %s.", $domain, $config{$key}{'server'});
-                next;
-            }
-            next if !header_ok($domain, $reply);
-
-            # Strip header
-            $reply =~ s/^.*?\n\n//s;
-            $response = eval { decode_json($reply) };
-            if (!defined $response || !defined $response->{result}) {
-                failed("invalid json or result.");
-                next;
-            }
-
-            # Pull the ID out of the json, messy
-            my ($dns_rec_id) = map { $_->{name} eq $domain ? $_->{id} : () } @{$response->{result}};
-            unless ($dns_rec_id) {
-                failed("updating %s: No DNS record ID found.", $domain);
-                next;
-            }
-            info("DNS record ID is %s", $dns_rec_id);
-
-            # Set domain
-            $url = "https://$config{$key}{'server'}/zones/$zone_id/dns_records/$dns_rec_id";
-            my $data = "{\"content\":\"$ip\"}";
-            $reply = geturl(
-                proxy => opt('proxy'),
-                url => $url,
-                headers => $headers,
-                method => "PATCH",
-                data => $data,
-            );
-            unless ($reply) {
-                failed("updating %s: Could not connect to %s.", $domain, $config{$domain}{'server'});
-                next;
-            }
-            next if !header_ok($domain, $reply);
-
-            # Strip header
-            $reply =~ s/^.*?\n\n//s;
-            $response = eval { decode_json($reply) };
-            if (!defined $response || !defined $response->{result}) {
-                failed("invalid json or result.");
-            } else {
-                success("%s -- Updated Successfully to %s", $domain, $ip);
-
-            }
-
-            # Cache
-            $config{$domain}{'ip'}     = $ip;
-            $config{$domain}{'mtime'}  = $now;
-            $config{$domain}{'status'} = 'good';
         }
     }
 }
+
 ######################################################################
 ## nic_yandex_examples
 ######################################################################
@@ -5329,13 +6390,13 @@ sub nic_gandi_update {
         $url  = "https://$config{$h}{'server'}$config{$h}{'script'}";
         $url .= "/livedns/domains/$config{$h}{'zone'}/records/$hostname/$rrset_type";
 
-        my $reply = geturl({
-            proxy   => opt('proxy'),
-            url     => $url,
-            headers => $headers,
-            method  => 'PUT',
-            data    => $data,
-        });
+        my $reply = geturl(
+            proxy    => opt('proxy'),
+            url      => $url,
+            headers  => $headers,
+            method   => 'PUT',
+            data     => $data,
+        );
         unless ($reply) {
             failed("%s -- Could not connect to %s.", $h, $config{$h}{'server'});
             next;
diff --git a/t/get_ip_from_if.pl b/t/get_ip_from_if.pl
new file mode 100644
index 0000000..6f08e5d
--- /dev/null
+++ b/t/get_ip_from_if.pl
@@ -0,0 +1,63 @@
+use Test::More;
+use ddclient::t;
+SKIP: { eval { require Test::Warnings; } or skip($@, 1); }
+eval { require 'ddclient'; } or BAIL_OUT($@);
+
+# To aid in debugging, uncomment the following lines. (They are normally left commented to avoid
+# accidentally interfering with the Test Anything Protocol messages written by Test::More.)
+#STDOUT->autoflush(1);
+#$ddclient::globals{'debug'} = 1;
+
+subtest "get_default_interface tests" => sub {
+    for my $sample (@ddclient::t::routing_samples) {
+        if (defined($sample->{want_ipv4_if})) {
+            my $interface = ddclient::get_default_interface(4, $sample->{text});
+            is($interface, $sample->{want_ipv4_if}, $sample->{name});
+        }
+        if (defined($sample->{want_ipv6_if})) {
+            my $interface = ddclient::get_default_interface(6, $sample->{text});
+            is($interface, $sample->{want_ipv6_if}, $sample->{name});
+        }
+    }
+};
+
+subtest "get_ip_from_interface tests" => sub {
+    for my $sample (@ddclient::t::interface_samples) {
+        # interface name is undef as we are passing in test data
+        if (defined($sample->{want_ipv4_from_if})) {
+            my $ip = ddclient::get_ip_from_interface(undef, 4, undef, $sample->{text}, $sample->{MacOS});
+            is($ip, $sample->{want_ipv4_from_if}, $sample->{name});
+        }
+        if (defined($sample->{want_ipv6gua_from_if})) {
+            my $ip = ddclient::get_ip_from_interface(undef, 6, 'gua', $sample->{text}, $sample->{MacOS});
+            is($ip, $sample->{want_ipv6gua_from_if}, $sample->{name});
+        }
+        if (defined($sample->{want_ipv6ula_from_if})) {
+            my $ip = ddclient::get_ip_from_interface(undef, 6, 'ula', $sample->{text}, $sample->{MacOS});
+            is($ip, $sample->{want_ipv6ula_from_if}, $sample->{name});
+        }
+    }
+};
+
+subtest "Get default interface and IP for test system" => sub {
+    my $interface = ddclient::get_default_interface(4);
+    if ($interface) {
+        isnt($interface, "lo", "Check for loopback 'lo'");
+        isnt($interface, "lo0", "Check for loopback 'lo0'");
+        my $ip1 = ddclient::get_ip_from_interface("default", 4);
+        my $ip2 = ddclient::get_ip_from_interface($interface, 4);
+        is($ip1, $ip2, "Check IPv4 from default interface");
+        ok(ddclient::is_ipv4($ip1), "Valid IPv4 from get_ip_from_interface($interface)");
+    }
+    $interface = ddclient::get_default_interface(6);
+    if ($interface) {
+        isnt($interface, "lo", "Check for loopback 'lo'");
+        isnt($interface, "lo0", "Check for loopback 'lo0'");
+        my $ip1 = ddclient::get_ip_from_interface("default", 6);
+        my $ip2 = ddclient::get_ip_from_interface($interface, 6);
+        is($ip1, $ip2, "Check IPv6 from default interface");
+        ok(ddclient::is_ipv6($ip1), "Valid IPv6 from get_ip_from_interface($interface)");
+    }
+};
+
+done_testing();
diff --git a/t/geturl_connectivity.pl b/t/geturl_connectivity.pl.in
similarity index 79%
rename from t/geturl_connectivity.pl
rename to t/geturl_connectivity.pl.in
index bc0d56b..2e825d0 100644
--- a/t/geturl_connectivity.pl
+++ b/t/geturl_connectivity.pl.in
@@ -13,6 +13,8 @@ my $ipv6_supported = eval {
     );
     defined($ipv6_socket);
 };
+my $has_curl = qx{ @CURL@ --version 2>/dev/null; } && $? == 0;
+
 my $http_daemon_supports_ipv6 = eval {
     require HTTP::Daemon;
     HTTP::Daemon->VERSION(6.12);
@@ -71,23 +73,39 @@ my @test_cases = (
     {ssl => 1, server_ipv => '4', client_ipv => '4'},
     {ssl => 1, server_ipv => '6', client_ipv => ''},
     {ssl => 1, server_ipv => '6', client_ipv => '6'},
+
+    # Fetch with curl
+    { curl => 1, server_ipv => '4', client_ipv => '' },
+    { curl => 1, server_ipv => '4', client_ipv => '4' },
+    { curl => 1, server_ipv => '6', client_ipv => '' },
+    { curl => 1, server_ipv => '6', client_ipv => '6' },
+
+    # Fetch with curl and ssl
+    { curl => 1, ssl => 1, server_ipv => '4', client_ipv => '' },
+    { curl => 1, ssl => 1, server_ipv => '4', client_ipv => '4' },
+    { curl => 1, ssl => 1, server_ipv => '6', client_ipv => '' },
+    { curl => 1, ssl => 1, server_ipv => '6', client_ipv => '6' },
 );
 
 for my $tc (@test_cases) {
     $tc->{ipv6_opt} //= 0;
     $tc->{ssl} //= 0;
+    $tc->{curl} //= 0;
     SKIP: {
         skip("IO::Socket::INET6 not available", 1)
-            if ($tc->{ipv6_opt} || $tc->{client_ipv} eq '6') && !$has_io_socket_inet6;
+            if ($tc->{ipv6_opt} || $tc->{client_ipv} eq '6') && !$tc->{curl} && !$has_io_socket_inet6;
         skip("IPv6 not supported on this system", 1)
             if $tc->{server_ipv} eq '6' && !$ipv6_supported;
         skip("HTTP::Daemon too old for IPv6 support", 1)
             if $tc->{server_ipv} eq '6' && !$http_daemon_supports_ipv6;
         skip("HTTP::Daemon::SSL not available", 1) if $tc->{ssl} && !$has_http_daemon_ssl;
+        skip("Curl not available on this system", 1) if $tc->{curl} && !$has_curl;
         my $uri = $httpd{$tc->{server_ipv}}{$tc->{ssl} ? 'https' : 'http'}->endpoint();
-        my $name = sprintf("IPv%s client to %s%s",
-                           $tc->{client_ipv} || '*', $uri, $tc->{ipv6_opt} ? ' (-ipv6)' : '');
+        my $name = sprintf("IPv%s client to %s%s%s",
+                           $tc->{client_ipv} || '*', $uri, $tc->{ipv6_opt} ? ' (-ipv6)' : '',
+                           $tc->{curl} ? ' (curl)' : '');
         $ddclient::globals{'ipv6'} = $tc->{ipv6_opt};
+        $ddclient::globals{'curl'} = $tc->{curl};
         my $got = ddclient::geturl(url => $uri, ipversion => $tc->{client_ipv});
         isnt($got // '', '', $name);
     }
diff --git a/t/geturl_ssl.pl b/t/geturl_ssl.pl
index 9b0212f..c070def 100644
--- a/t/geturl_ssl.pl
+++ b/t/geturl_ssl.pl
@@ -4,6 +4,7 @@ eval {
     require HTTP::Request;
     require HTTP::Response;
     require IO::Socket::IP;
+    require IO::Socket::SSL;
     require ddclient::Test::Fake::HTTPD;
 } or plan(skip_all => $@);
 SKIP: { eval { require Test::Warnings; } or skip($@, 1); }
@@ -57,6 +58,7 @@ my @test_cases = (
         want_args => {
             PeerAddr => 'hostname',
             PeerPort => '443',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => '/',
     },
@@ -69,6 +71,7 @@ my @test_cases = (
         want_args => {
             PeerAddr => 'hostname',
             PeerPort => '443',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => '/',
     },
@@ -80,6 +83,7 @@ my @test_cases = (
         want_args => {
             PeerAddr => 'hostname',
             PeerPort => '123',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => '/',
     },
@@ -92,6 +96,7 @@ my @test_cases = (
         want_args => {
             PeerAddr => 'hostname',
             PeerPort => '123',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => '/',
     },
@@ -104,6 +109,7 @@ my @test_cases = (
         want_args => {
             PeerAddr => 'proxy',
             PeerPort => '443',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => 'http://hostname/',
         todo => "broken",
@@ -132,6 +138,7 @@ my @test_cases = (
         want_args => {
             PeerAddr => 'proxy',
             PeerPort => '443',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_method => 'CONNECT',
         want_req_uri => 'hostname:443',
@@ -147,6 +154,7 @@ my @test_cases = (
         want_args => {
             PeerAddr => 'proxy',
             PeerPort => '443',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_method => 'CONNECT',
         want_req_uri => 'hostname:443',
@@ -190,6 +198,7 @@ my @test_cases = (
             PeerAddr => 'hostname',
             PeerPort => '443',
             SSL_ca_path => '/ca/dir',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => '/',
     },
@@ -203,6 +212,7 @@ my @test_cases = (
             PeerAddr => 'hostname',
             PeerPort => '443',
             SSL_ca_file => '/ca/file',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => '/',
     },
@@ -218,6 +228,7 @@ my @test_cases = (
             PeerPort => '443',
             SSL_ca_file => '/ca/file',
             SSL_ca_path => '/ca/dir',
+            SSL_verify_mode => IO::Socket::SSL->SSL_VERIFY_PEER,
         },
         want_req_uri => '/',
     },
diff --git a/t/is-and-extract-ipv6-global.pl b/t/is-and-extract-ipv6-global.pl
index de7a991..b0e660e 100644
--- a/t/is-and-extract-ipv6-global.pl
+++ b/t/is-and-extract-ipv6-global.pl
@@ -56,8 +56,10 @@ subtest "extract_ipv6_global()" => sub {
 
 subtest "interface config samples" => sub {
     for my $sample (@ddclient::t::interface_samples) {
-        my $got = ddclient::extract_ipv6_global($sample->{text});
-        is($got, $sample->{want_extract_ipv6_global}, $sample->{name});
+        if (defined($sample->{want_extract_ipv6_global})) {
+            my $got = ddclient::extract_ipv6_global($sample->{text});
+            is($got, $sample->{want_extract_ipv6_global}, $sample->{name});
+        }
     }
 };
 
diff --git a/t/is-and-extract-ipv6.pl b/t/is-and-extract-ipv6.pl
index a7d97b9..7362be6 100644
--- a/t/is-and-extract-ipv6.pl
+++ b/t/is-and-extract-ipv6.pl
@@ -422,13 +422,17 @@ subtest "extract_ipv6() of valid addr with adjacent non-word char" => sub {
 
 subtest "interface config samples" => sub {
     for my $sample (@ddclient::t::interface_samples) {
-        subtest $sample->{name} => sub {
-            my $ip = ddclient::extract_ipv6($sample->{text});
-            ok(ddclient::is_ipv6($ip), "extract_ipv6() returns an IPv6 address");
+        if (defined($sample->{want_extract_ipv6_global})) {
+            subtest $sample->{name} => sub {
+                my $ip = ddclient::extract_ipv6($sample->{text});
+                ok(ddclient::is_ipv6($ip), "extract_ipv6() returns an IPv6 address");
+            };
             foreach my $line (split(/\n/, $sample->{text})) {
                 my $ip = ddclient::extract_ipv6($line);
-                ok(ddclient::is_ipv6($ip),
-                   sprintf("extract_ipv6(%s) returns an IPv6 address", perlstring($line)));
+                if ($ip) {  ## Test cases may have lines that do not contain IPv6 address.
+                    ok(ddclient::is_ipv6($ip),
+                       sprintf("extract_ipv6(%s) returns an IPv6 address", perlstring($line)));
+                }
             }
         }
     }
diff --git a/t/lib/ddclient/t.pm b/t/lib/ddclient/t.pm
index 2468b73..c546b9c 100644
--- a/t/lib/ddclient/t.pm
+++ b/t/lib/ddclient/t.pm
@@ -3,54 +3,62 @@ require v5.10.1;
 use strict;
 use warnings;
 
+
+######################################################################
+## Outputs from ip addr and ifconfig commands to find IP address from IF name
+## Samples from Ubuntu 20.04, RHEL8, Buildroot, Busybox, MacOS 10.15, FreeBSD
+## NOTE: Any tabs/whitespace at start or end of lines are intentional to match real life data.
+######################################################################
 our @interface_samples = (
-    # Sample output from:
-    #   ip -6 -o addr show dev <interface> scope global
     # This seems to be consistent accross platforms. The last line is from Ubuntu of a static
     # assigned IPv6.
     {
         name => 'ip -6 -o addr show dev <interface> scope global',
         text => <<'EOF',
 2: ens160    inet6 fdb6:1d86:d9bd:1::8214/128 scope global dynamic noprefixroute \       valid_lft 63197sec preferred_lft 63197sec
-2: ens160    inet6 2001:DB8:4341:0781::8214/128 scope global dynamic noprefixroute \       valid_lft 63197sec preferred_lft 63197sec
-2: ens160    inet6 2001:DB8:4341:0781:89b9:4b1c:186c:a0c7/64 scope global temporary dynamic \       valid_lft 85954sec preferred_lft 21767sec
+2: ens160    inet6 2001:db8:4341:0781::8214/128 scope global dynamic noprefixroute \       valid_lft 63197sec preferred_lft 63197sec
+2: ens160    inet6 2001:db8:4341:0781:89b9:4b1c:186c:a0c7/64 scope global temporary dynamic \       valid_lft 85954sec preferred_lft 21767sec
 2: ens160    inet6 fdb6:1d86:d9bd:1:89b9:4b1c:186c:a0c7/64 scope global temporary dynamic \       valid_lft 85954sec preferred_lft 21767sec
 2: ens160    inet6 fdb6:1d86:d9bd:1:34a6:c329:c52e:8ba6/64 scope global temporary deprecated dynamic \       valid_lft 85954sec preferred_lft 0sec
 2: ens160    inet6 fdb6:1d86:d9bd:1:b417:fe35:166b:4816/64 scope global dynamic mngtmpaddr noprefixroute \       valid_lft 85954sec preferred_lft 85954sec
-2: ens160    inet6 2001:DB8:4341:0781:34a6:c329:c52e:8ba6/64 scope global temporary deprecated dynamic \       valid_lft 85954sec preferred_lft 0sec
-2: ens160    inet6 2001:DB8:4341:0781:f911:a224:7e69:d22/64 scope global dynamic mngtmpaddr noprefixroute \       valid_lft 85954sec preferred_lft 85954sec
-2: ens160    inet6 2001:DB8:4341:0781::100/128 scope global noprefixroute \       valid_lft forever preferred_lft forever
+2: ens160    inet6 2001:db8:4341:0781:34a6:c329:c52e:8ba6/64 scope global temporary deprecated dynamic \       valid_lft 85954sec preferred_lft 0sec
+2: ens160    inet6 2001:db8:4341:0781:f911:a224:7e69:d22/64 scope global dynamic mngtmpaddr noprefixroute \       valid_lft 85954sec preferred_lft 85954sec
+2: ens160    inet6 2001:db8:4341:0781::100/128 scope global noprefixroute \       valid_lft forever preferred_lft forever
 EOF
-        want_extract_ipv6_global => '2001:DB8:4341:781::8214',
+        want_extract_ipv6_global => '2001:db8:4341:781::8214',
+        want_ipv6gua_from_if => "2001:db8:4341:781::100",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:1::8214",
     },
-    # Sample output from MacOS:
-    #   ifconfig <interface> | grep -w "inet6"
-    # (Yes, there is a tab at start of each line.) The last two lines are with a manually
+    # (Yes, there is a tab at start of each line.) The last lines is with a manually
     # configured static GUA.
     {
         name => 'MacOS: ifconfig <interface> | grep -w inet6',
+        MacOS => 1,
         text => <<'EOF',
 	inet6 fe80::1419:abd0:5943:8bbb%en0 prefixlen 64 secured scopeid 0xa
 	inet6 fdb6:1d86:d9bd:1:142c:8e9e:de48:843e prefixlen 64 autoconf secured
 	inet6 fdb6:1d86:d9bd:1:7447:cf67:edbd:cea4 prefixlen 64 autoconf temporary
 	inet6 fdb6:1d86:d9bd:1::c5b3 prefixlen 64 dynamic
-	inet6 2001:DB8:4341:0781:141d:66b9:2ba1:b67d prefixlen 64 autoconf secured
-	inet6 2001:DB8:4341:0781:64e1:b68f:e8af:5d6e prefixlen 64 autoconf temporary
-	inet6 fe80::1419:abd0:5943:8bbb%en0 prefixlen 64 secured scopeid 0xa
-	inet6 2001:DB8:4341:0781::101 prefixlen 64
+	inet6 2001:db8:4341:0781:141d:66b9:2ba1:b67d prefixlen 64 autoconf secured
+	inet6 2001:db8:4341:0781:64e1:b68f:e8af:5d6e prefixlen 64 autoconf temporary
+	inet6 2001:db8:4341:0781::101 prefixlen 64
 EOF
-        want_extract_ipv6_global => '2001:DB8:4341:781:141d:66b9:2ba1:b67d',
+        want_extract_ipv6_global => '2001:db8:4341:781:141d:66b9:2ba1:b67d',
+        want_ipv6gua_from_if => "2001:db8:4341:781::101",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:1::c5b3",
     },
     {
         name => 'RHEL: ifconfig <interface> | grep -w inet6',
         text => <<'EOF',
-        inet6 2001:DB8:4341:0781::dc14  prefixlen 128  scopeid 0x0<global>
+        inet6 2001:db8:4341:0781::dc14  prefixlen 128  scopeid 0x0<global>
         inet6 fe80::cd48:4a58:3b0f:4d30  prefixlen 64  scopeid 0x20<link>
-        inet6 2001:DB8:4341:0781:e720:3aec:a936:36d4  prefixlen 64  scopeid 0x0<global>
+        inet6 2001:db8:4341:0781:e720:3aec:a936:36d4  prefixlen 64  scopeid 0x0<global>
         inet6 fdb6:1d86:d9bd:1:9c16:8cbf:ae33:f1cc  prefixlen 64  scopeid 0x0<global>
         inet6 fdb6:1d86:d9bd:1::dc14  prefixlen 128  scopeid 0x0<global>
 EOF
-        want_extract_ipv6_global => '2001:DB8:4341:781::dc14',
+        want_extract_ipv6_global => '2001:db8:4341:781::dc14',
+        want_ipv6gua_from_if => "2001:db8:4341:781::dc14",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:1::dc14",
     },
     {
         name => 'Ubuntu: ifconfig <interface> | grep -w inet6',
@@ -60,19 +68,495 @@ EOF
         inet6 fdb6:1d86:d9bd:1::8214  prefixlen 128  scopeid 0x0<global>
         inet6 fdb6:1d86:d9bd:1:b417:fe35:166b:4816  prefixlen 64  scopeid 0x0<global>
         inet6 fe80::5b31:fc63:d353:da68  prefixlen 64  scopeid 0x20<link>
-        inet6 2001:DB8:4341:0781::8214  prefixlen 128  scopeid 0x0<global>
-        inet6 2001:DB8:4341:0781:34a6:c329:c52e:8ba6  prefixlen 64  scopeid 0x0<global>
-        inet6 2001:DB8:4341:0781:89b9:4b1c:186c:a0c7  prefixlen 64  scopeid 0x0<global>
-        inet6 2001:DB8:4341:0781:f911:a224:7e69:d22  prefixlen 64  scopeid 0x0<global>
+        inet6 2001:db8:4341:0781::8214  prefixlen 128  scopeid 0x0<global>
+        inet6 2001:db8:4341:0781:34a6:c329:c52e:8ba6  prefixlen 64  scopeid 0x0<global>
+        inet6 2001:db8:4341:0781:89b9:4b1c:186c:a0c7  prefixlen 64  scopeid 0x0<global>
+        inet6 2001:db8:4341:0781:f911:a224:7e69:d22  prefixlen 64  scopeid 0x0<global>
 EOF
-        want_extract_ipv6_global => '2001:DB8:4341:781::8214',
+        want_extract_ipv6_global => '2001:db8:4341:781::8214',
+        want_ipv6gua_from_if => "2001:db8:4341:781::8214",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:1::8214",
     },
     {
         name => 'Busybox: ifconfig <interface> | grep -w inet6',
         text => <<'EOF',
           inet6 addr: fe80::4362:31ff:fe08:61b4/64 Scope:Link
-          inet6 addr: 2001:DB8:4341:0781:ed44:eb63:b070:212f/128 Scope:Global
+          inet6 addr: 2001:db8:4341:781:ed44:eb63:b070:212f/128 Scope:Global
 EOF
-        want_extract_ipv6_global => '2001:DB8:4341:781:ed44:eb63:b070:212f',
+        want_extract_ipv6_global => '2001:db8:4341:781:ed44:eb63:b070:212f',
+        want_ipv6gua_from_if => "2001:db8:4341:781:ed44:eb63:b070:212f",
+    },
+    {   name => "ip -4 -o addr show dev ens33 scope global (most linux IPv4)",
+        text => <<EOF,
+2: ens33    inet 198.51.100.33/24 brd 198.51.100.255 scope global dynamic noprefixroute ens33\       valid_lft 77760sec preferred_lft 77760sec
+EOF
+        want_ipv4_from_if => "198.51.100.33",
+    },
+    {   name => "ip -6 -o addr show dev ens33 scope global (most linux)",
+        text => <<EOF,
+2: ens33    inet6 2001:db8:450a:e723:adee:be82:7fba:ffb2/64 scope global temporary dynamic \       valid_lft 86282sec preferred_lft 81094sec
+2: ens33    inet6 fdb6:1d86:d9bd:3:adee:be82:7fba:ffb2/64 scope global temporary dynamic \       valid_lft 86282sec preferred_lft 81094sec
+2: ens33    inet6 fdb6:1d86:d9bd:3::21/128 scope global dynamic noprefixroute \       valid_lft 76832sec preferred_lft 76832sec
+2: ens33    inet6 2001:db8:450a:e723::21/128 scope global dynamic noprefixroute \       valid_lft 76832sec preferred_lft 76832sec
+2: ens33    inet6 fdb6:1d86:d9bd:3:514:cbd9:c55f:8e2a/64 scope global temporary deprecated dynamic \       valid_lft 86282sec preferred_lft 0sec
+2: ens33    inet6 fdb6:1d86:d9bd:3:a1fd:1ed9:6211:4268/64 scope global dynamic mngtmpaddr noprefixroute \       valid_lft 86282sec preferred_lft 86282sec
+2: ens33    inet6 2001:db8:450a:e723:514:cbd9:c55f:8e2a/64 scope global temporary deprecated dynamic \       valid_lft 86282sec preferred_lft 0sec
+2: ens33    inet6 2001:db8:450a:e723:dbc5:1c4e:9e9b:97a2/64 scope global dynamic mngtmpaddr noprefixroute \       valid_lft 86282sec preferred_lft 86282sec
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723:adee:be82:7fba:ffb2",
+        want_ipv6gua_from_if => "2001:db8:450a:e723::21",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:3::21",
+    },
+    {   name => "ip -6 -o addr show dev ens33 scope global (most linux static IPv6)",
+        text => <<EOF,
+2: ens33    inet6 2001:db8:450a:e723::101/64 scope global noprefixroute \       valid_lft forever preferred_lft forever
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723::101",
+        want_ipv6gua_from_if => "2001:db8:450a:e723::101",
+    },
+    {   name => "ifconfig ens33 (most linux autoconf IPv6 and DHCPv6)",
+        text => <<EOF,
+ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
+        inet 198.51.100.33  netmask 255.255.255.0  broadcast 198.51.100.255
+        inet6 fdb6:1d86:d9bd:3::21  prefixlen 128  scopeid 0x0<global>
+        inet6 fe80::32c0:b270:245b:d3b4  prefixlen 64  scopeid 0x20<link>
+        inet6 fdb6:1d86:d9bd:3:a1fd:1ed9:6211:4268  prefixlen 64  scopeid 0x0<global>
+        inet6 2001:db8:450a:e723:adee:be82:7fba:ffb2  prefixlen 64  scopeid 0x0<global>
+        inet6 2001:db8:450a:e723::21  prefixlen 128  scopeid 0x0<global>
+        inet6 fdb6:1d86:d9bd:3:adee:be82:7fba:ffb2  prefixlen 64  scopeid 0x0<global>
+        inet6 2001:db8:450a:e723:dbc5:1c4e:9e9b:97a2  prefixlen 64  scopeid 0x0<global>
+        ether 00:00:00:da:24:b1  txqueuelen 1000  (Ethernet)
+        RX packets 3782541  bytes 556082941 (556.0 MB)
+        RX errors 0  dropped 513  overruns 0  frame 0
+        TX packets 33294  bytes 6838768 (6.8 MB)
+        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723:adee:be82:7fba:ffb2",
+        want_ipv6gua_from_if => "2001:db8:450a:e723::21",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:3::21",
+        want_ipv4_from_if => "198.51.100.33",
+    },
+    {   name => "ifconfig ens33 (most linux DHCPv6)",
+        text => <<EOF,
+ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
+        inet 198.51.100.33  netmask 255.255.255.0  broadcast 198.51.100.255
+        inet6 fdb6:1d86:d9bd:3::21  prefixlen 128  scopeid 0x0<global>
+        inet6 fe80::32c0:b270:245b:d3b4  prefixlen 64  scopeid 0x20<link>
+        inet6 2001:db8:450a:e723::21  prefixlen 128  scopeid 0x0<global>
+        ether 00:00:00:da:24:b1  txqueuelen 1000  (Ethernet)
+        RX packets 3781554  bytes 555602847 (555.6 MB)
+        RX errors 0  dropped 513  overruns 0  frame 0
+        TX packets 32493  bytes 6706131 (6.7 MB)
+        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723::21",
+        want_ipv6gua_from_if => "2001:db8:450a:e723::21",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:3::21",
+        want_ipv4_from_if => "198.51.100.33",
+    },
+    {   name => "ifconfig ens33 (most linux static IPv6)",
+        text => <<EOF,
+ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
+        inet 198.51.100.33  netmask 255.255.255.0  broadcast 198.51.100.255
+        inet6 fe80::32c0:b270:245b:d3b4  prefixlen 64  scopeid 0x20<link>
+        inet6 2001:db8:450a:e723::101  prefixlen 64  scopeid 0x0<global>
+        ether 00:00:00:da:24:b1  txqueuelen 1000  (Ethernet)
+        RX packets 3780219  bytes 554967876 (554.9 MB)
+        RX errors 0  dropped 513  overruns 0  frame 0
+        TX packets 31556  bytes 6552122 (6.5 MB)
+        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723::101",
+        want_ipv6gua_from_if => "2001:db8:450a:e723::101",
+        want_ipv4_from_if => "198.51.100.33",
+    },
+    {   name => "ifconfig en0 (MacOS IPv4)",
+        text => <<EOF,
+en0: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 9000
+	options=50b<RXCSUM,TXCSUM,VLAN_HWTAGGING,AV,CHANNEL_IO>
+	ether 00:00:00:90:32:8f 
+	inet6 fe80::85b:d150:cdd9:3198%en0 prefixlen 64 secured scopeid 0x4 
+	inet6 2001:db8:450a:e723:1c99:99e2:21d0:79e6 prefixlen 64 autoconf secured 
+	inet6 2001:db8:450a:e723:808d:d894:e4db:157e prefixlen 64 deprecated autoconf temporary 
+	inet6 fdb6:1d86:d9bd:3:837:e1c7:4895:269e prefixlen 64 autoconf secured 
+	inet6 fdb6:1d86:d9bd:3:a0b3:aa4d:9e76:e1ab prefixlen 64 deprecated autoconf temporary 
+	inet 198.51.100.5 netmask 0xffffff00 broadcast 198.51.100.255
+	inet6 2001:db8:450a:e723:2474:39fd:f5c0:6845 prefixlen 64 autoconf temporary 
+	inet6 fdb6:1d86:d9bd:3:2474:39fd:f5c0:6845 prefixlen 64 autoconf temporary 
+	inet6 fdb6:1d86:d9bd:3::8076 prefixlen 64 dynamic 
+	nd6 options=201<PERFORMNUD,DAD>
+	media: 1000baseT <full-duplex,flow-control,energy-efficient-ethernet>
+	status: active
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723:1c99:99e2:21d0:79e6",
+        want_ipv6gua_from_if => "2001:db8:450a:e723:1c99:99e2:21d0:79e6",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:3::8076",
+        want_ipv4_from_if => "198.51.100.5",
+    },
+    {   name => "ifconfig em0 (FreeBSD IPv4)",
+        text => <<EOF,
+em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
+	options=81009b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,VLAN_HWFILTER>
+	ether 00:00:00:9f:c5:32
+	inet6 fe80::20c:29ff:fe9f:c532%em0 prefixlen 64 scopeid 0x1
+	inet6 2001:db8:450a:e723:20c:29ff:fe9f:c532 prefixlen 64 autoconf
+	inet6 fdb6:1d86:d9bd:3:20c:29ff:fe9f:c532 prefixlen 64 autoconf
+	inet 198.51.100.207 netmask 0xffffff00 broadcast 198.51.100.255
+	media: Ethernet autoselect (1000baseT <full-duplex>)
+	status: active
+	nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723:20c:29ff:fe9f:c532",
+        want_ipv6gua_from_if => "2001:db8:450a:e723:20c:29ff:fe9f:c532",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:3:20c:29ff:fe9f:c532",
+        want_ipv4_from_if => "198.51.100.207",
+    },
+    {   name => "ifconfig -L en0 (MacOS autoconf IPv6)",
+        MacOS => 1,
+        text => <<EOF,
+en0: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 9000
+	options=50b<RXCSUM,TXCSUM,VLAN_HWTAGGING,AV,CHANNEL_IO>
+	ether 00:00:00:90:32:8f 
+	inet6 fe80::85b:d150:cdd9:3198%en0 prefixlen 64 secured scopeid 0x4 
+	inet6 2001:db8:450a:e723:1c99:99e2:21d0:79e6 prefixlen 64 autoconf secured pltime 86205 vltime 86205 
+	inet6 2001:db8:450a:e723:808d:d894:e4db:157e prefixlen 64 deprecated autoconf temporary pltime 0 vltime 86205 
+	inet6 fdb6:1d86:d9bd:3:837:e1c7:4895:269e prefixlen 64 autoconf secured pltime 86205 vltime 86205 
+	inet6 fdb6:1d86:d9bd:3:a0b3:aa4d:9e76:e1ab prefixlen 64 deprecated autoconf temporary pltime 0 vltime 86205 
+	inet 198.51.100.5 netmask 0xffffff00 broadcast 198.51.100.255
+	inet6 2001:db8:450a:e723:2474:39fd:f5c0:6845 prefixlen 64 autoconf temporary pltime 76882 vltime 86205 
+	inet6 fdb6:1d86:d9bd:3:2474:39fd:f5c0:6845 prefixlen 64 autoconf temporary pltime 76882 vltime 86205 
+	inet6 fdb6:1d86:d9bd:3::8076 prefixlen 64 dynamic pltime 78010 vltime 78010 
+	nd6 options=201<PERFORMNUD,DAD>
+	media: 1000baseT <full-duplex,flow-control,energy-efficient-ethernet>
+	status: active
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723:1c99:99e2:21d0:79e6",
+        want_ipv6gua_from_if => "2001:db8:450a:e723:1c99:99e2:21d0:79e6",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:3::8076",
+        want_ipv4_from_if => "198.51.100.5",
+    },
+    {   name => "ifconfig -L en0 (MacOS static IPv6)",
+        MacOS => 1,
+        text => <<EOF,
+en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
+	options=400<CHANNEL_IO>
+	ether 00:00:00:42:96:eb 
+	inet 198.51.100.199 netmask 0xffffff00 broadcast 198.51.100.255
+	inet6 fe80::1445:78b9:1d5c:11eb%en1 prefixlen 64 secured scopeid 0x5 
+	inet6 2001:db8:450a:e723::100 prefixlen 64 
+	nd6 options=201<PERFORMNUD,DAD>
+	media: autoselect
+	status: active
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723::100",
+        want_ipv6gua_from_if => "2001:db8:450a:e723::100",
+        want_ipv4_from_if => "198.51.100.199",
+    },
+    {   name => "ifconfig -L em0 (FreeBSD autoconf IPv6)",
+        MacOS => 1,
+        text => <<EOF,
+em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
+	options=81009b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,VLAN_HWFILTER>
+	ether 00:00:00:9f:c5:32
+	inet6 fe80::20c:29ff:fe9f:c532%em0 prefixlen 64 scopeid 0x1
+	inet6 2001:db8:450a:e723:20c:29ff:fe9f:c532 prefixlen 64 autoconf pltime 86114 vltime 86114
+	inet6 fdb6:1d86:d9bd:3:20c:29ff:fe9f:c532 prefixlen 64 autoconf pltime 86114 vltime 86114
+	inet 198.51.100.207 netmask 0xffffff00 broadcast 198.51.100.255
+	media: Ethernet autoselect (1000baseT <full-duplex>)
+	status: active
+	nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
+EOF
+        want_extract_ipv6_global => "2001:db8:450a:e723:20c:29ff:fe9f:c532",
+        want_ipv6gua_from_if => "2001:db8:450a:e723:20c:29ff:fe9f:c532",
+        want_ipv6ula_from_if => "fdb6:1d86:d9bd:3:20c:29ff:fe9f:c532",
+        want_ipv4_from_if => "198.51.100.207",
+    },
+    {   name => "ip -4 -o addr show dev eth0 scope global (Buildroot IPv4)",
+        text => <<EOF,
+2: eth0    inet 198.51.157.237/22 brd 255.255.255.255 scope global eth0\       valid_lft forever preferred_lft forever
+EOF
+        want_ipv4_from_if => "198.51.157.237",
+    },
+    {   name => "ip -6 -o addr show dev eth0 scope global (Buildroot IPv6)",
+        text => <<EOF,
+2: eth0    inet6 2001:db8:450b:13f:ed44:eb63:b070:212f/128 scope global \       valid_lft forever preferred_lft forever
+EOF
+        want_extract_ipv6_global => "2001:db8:450b:13f:ed44:eb63:b070:212f",
+        want_ipv6gua_from_if => "2001:db8:450b:13f:ed44:eb63:b070:212f",
+    },
+    {   name => "ifconfig eth0 (Busybox)",
+        text => <<EOF,
+eth0      Link encap:Ethernet  HWaddr 00:00:00:08:60:B4  
+          inet addr:198.51.157.237  Bcast:255.255.255.255  Mask:255.255.252.0
+          inet6 addr: fe80::4262:31ff:fe08:60b4/64 Scope:Link
+          inet6 addr: 2001:db8:450b:13f:ed44:eb63:b070:212f/128 Scope:Global
+          UP BROADCAST RUNNING MULTICAST  MTU:9000  Metric:1
+          RX packets:33209620 errors:0 dropped:0 overruns:0 frame:0
+          TX packets:14638979 errors:0 dropped:0 overruns:0 carrier:0
+          collisions:0 txqueuelen:1000 
+          RX bytes:41724254079 (38.8 GiB)  TX bytes:3221012240 (2.9 GiB)
+EOF
+        want_extract_ipv6_global => "2001:db8:450b:13f:ed44:eb63:b070:212f",
+        want_ipv6gua_from_if => "2001:db8:450b:13f:ed44:eb63:b070:212f",
+        want_ipv4_from_if => "198.51.157.237",
+    },
+);
+
+######################################################################
+## Outputs from ip route and netstat commands to find default route (and therefore interface)
+## Samples from Ubuntu 20.04, RHEL8, Buildroot, Busybox, MacOS 10.15, FreeBSD
+## NOTE: Any tabs/whitespace at start or end of lines are intentional to match real life data.
+######################################################################
+our @routing_samples = (
+    {   name => "ip -4 -o route list match default (most linux)",
+        text => <<EOF,
+default via 198.51.100.1 dev ens33 proto dhcp metric 100 
+EOF
+        want_ipv4_if => "ens33",
+    },
+    {   name => "ip -4 -o route list match default (most linux)",
+        text => <<EOF,
+default via fe80::4262:31ff:fe08:60b3 dev ens33 proto ra metric 20100 pref medium
+EOF
+        want_ipv4_if => "ens33",
+    },
+    {   name => "ip -4 -o route list match default (buildroot)",
+        text => <<EOF,
+default via 198.51.156.1 dev eth0 
+EOF
+        want_ipv4_if => "eth0",
+    },
+    {   name => "ip -6 -o route list match default (buildroot)",
+        text => <<EOF,
+default via fe80::1ee8:5dff:fef4:b822 dev eth0  proto ra  metric 1024  expires 1797sec mtu 1500 hoplimit 64
+EOF
+        want_ipv6_if => "eth0",
+    },
+    {   name => "netstat -rn -4 (most linux)",
+        text => <<EOF,
+Kernel IP routing table
+Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
+0.0.0.0         198.51.100.1    0.0.0.0         UG        0 0          0 ens33
+169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 ens33
+198.51.100.0    0.0.0.0         255.255.255.0   U         0 0          0 ens33
+EOF
+        want_ipv4_if => "ens33",
+    },
+    {   name => "netstat -rn -4 (FreeBSD)",
+        text => <<EOF,
+Routing tables
+
+Internet:
+Destination        Gateway            Flags     Netif Expire
+default            198.51.100.1       UGS         em0
+127.0.0.1          link#2             UH          lo0
+198.51.100.0/24    link#1             U           em0
+198.51.100.207     link#1             UHS         lo0
+EOF
+        want_ipv4_if => "em0",
+    },
+    {   name => "netstat -rn -6 (FreeBSD)",
+        text => <<EOF,
+Routing tables
+
+Internet6:
+Destination                       Gateway                       Flags     Netif Expire
+::/96                             ::1                           UGRS        lo0
+default                           fe80::4262:31ff:fe08:60b3%em0 UG          em0
+::1                               link#2                        UH          lo0
+::ffff:0.0.0.0/96                 ::1                           UGRS        lo0
+2001:db8:450a:e723::/64           link#1                        U           em0
+2001:db8:450a:e723:20c:29ff:fe9f:c532 link#1                    UHS         lo0
+fdb6:1d86:d9bd:3::/64             link#1                        U           em0
+fdb6:1d86:d9bd:3:20c:29ff:fe9f:c532 link#1                      UHS         lo0
+fe80::/10                         ::1                           UGRS        lo0
+fe80::%em0/64                     link#1                        U           em0
+fe80::20c:29ff:fe9f:c532%em0      link#1                        UHS         lo0
+fe80::%lo0/64                     link#2                        U           lo0
+fe80::1%lo0                       link#2                        UHS         lo0
+ff02::/16                         ::1                           UGRS        lo0
+EOF
+        want_ipv6_if => "em0",
+    },
+    {   name => "netstat -rn -6 (most linux)",
+        text => <<EOF,
+Kernel IPv6 routing table
+Destination                    Next Hop                   Flag Met Ref Use If
+::1/128                        ::                         U    256 2     0 lo
+2001:db8:450a:e723::21/128     ::                         U    100 1     0 ens33
+2001:db8:450a:e723::/64        ::                         U    100 4     0 ens33
+fdb6:1d86:d9bd:3::21/128       ::                         U    100 1     0 ens33
+fdb6:1d86:d9bd:3::/64          ::                         U    100 3     0 ens33
+fe80::/64                      ::                         U    100 2     0 ens33
+::/0                           fe80::4262:31ff:fe08:60b3  UG   20100 5     0 ens33
+::1/128                        ::                         Un   0   4     0 lo
+2001:db8:450a:e723::21/128     ::                         Un   0   4     0 ens33
+2001:db8:450a:e723:514:cbd9:c55f:8e2a/128 ::                         Un   0   4     0 ens33
+2001:db8:450a:e723:adee:be82:7fba:ffb2/128 ::                         Un   0   3     0 ens33
+2001:db8:450a:e723:dbc5:1c4e:9e9b:97a2/128 ::                         Un   0   3     0 ens33
+fdb6:1d86:d9bd:3::21/128       ::                         Un   0   2     0 ens33
+fdb6:1d86:d9bd:3:514:cbd9:c55f:8e2a/128 ::                         Un   0   5     0 ens33
+fdb6:1d86:d9bd:3:a1fd:1ed9:6211:4268/128 ::                         Un   0   4     0 ens33
+fdb6:1d86:d9bd:3:adee:be82:7fba:ffb2/128 ::                         Un   0   2     0 ens33
+fe80::32c0:b270:245b:d3b4/128  ::                         Un   0   3     0 ens33
+ff00::/8                       ::                         U    256 7     0 ens33
+::/0                           ::                         !n   -1  1     0 lo
+EOF
+        want_ipv6_if => "ens33",
+    },
+    {   name => "netstat -rn -f inet (MacOS)",
+        text => <<EOF,
+Routing tables
+
+Internet:
+Destination        Gateway            Flags        Netif Expire
+default            198.51.100.1       UGSc           en0       
+default            198.51.100.1       UGScI          en1       
+127                127.0.0.1          UCS            lo0       
+127.0.0.1          127.0.0.1          UH             lo0       
+169.254            link#4             UCS            en0      !
+169.254            link#5             UCSI           en1      !
+172.16.114/24      link#15            UC          vmnet8      !
+172.16.114.1       0:50:56:c0:0:8     UHLWIi         lo0       
+172.16.114.255     ff:ff:ff:ff:ff:ff  UHLWbI      vmnet8      !
+198.51.17         link#4             UCS            en0      !
+198.51.17         link#5             UCSI           en1      !
+198.51.100.1/32    link#4             UCS            en0      !
+198.51.100.1       40:62:31:8:60:b3   UHLWIir        en0   1180
+198.51.100.1       40:62:31:8:60:b3   UHLWIir        en1   1160
+198.51.100.1/32    link#5             UCSI           en1      !
+198.51.100.2       0:c:29:47:b8:d1    UHLWI          en0   1108
+198.51.100.5/32    link#4             UCS            en0      !
+198.51.100.5       00:00:00:90:32:8f  UHLWIi         lo0       
+198.51.100.5       00:00:00:90:32:8f  UHLWI          en1   1182
+198.51.100.6       0:8:9b:ee:d4:e     UHLWIi         en0    158
+198.51.100.12      0:c:29:70:89:8b    UHLWI          en0   1107
+198.51.100.33      0:c:29:da:24:b1    UHLWI          en0   1108
+198.51.100.34      0:c:29:6d:aa:8b    UHLWI          en0   1107
+198.51.100.137     70:ea:5a:79:45:4b  UHLWI          en0    317
+198.51.100.137     70:ea:5a:79:45:4b  UHLWI          en1    561
+198.51.100.152     8c:79:67:a7:c4:45  UHLWI          en0    376
+198.51.100.155     f0:18:98:29:ef:a3  UHLWIi         en0    694
+198.51.100.167     a0:2:dc:f7:7a:9a   UHLWI          en0   1160
+198.51.100.167     a0:2:dc:f7:7a:9a   UHLWI          en1   1161
+198.51.100.184     8:66:98:92:0:55    UHLWIi         en0    644
+198.51.100.187     link#4             UHLWIi         en0      !
+198.51.100.187     link#5             UHLWIi         en1      !
+198.51.100.199/32  link#5             UCS            en1      !
+198.51.100.199     c8:e0:eb:42:96:eb  UHLWIi         lo0       
+198.51.100.201     90:e1:7b:b9:e5:38  UHLWI          en0   1182
+198.51.100.201     90:e1:7b:b9:e5:38  UHLWI          en1   1182
+198.51.100.210     0:61:71:cd:0:10    UHLWI          en0    112
+198.51.100.210     0:61:71:cd:0:10    UHLWI          en1    112
+198.51.100.211     8c:85:90:55:49:a7  UHLWIi         en0    762
+198.51.100.211     8c:85:90:55:49:a7  UHLWI          en1    762
+198.51.100.240     f0:18:98:20:f9:d7  UHLWIi         en0   1172
+198.51.100.240     f0:18:98:20:f9:d7  UHLWIi         en1   1173
+198.51.100.241     e0:33:8e:38:44:3   UHLWIi         en0    961
+198.51.100.241     e0:33:8e:38:44:3   UHLWI          en1    961
+198.51.100.242     98:1:a7:49:1e:1c   UHLWIi         en0    899
+198.51.100.242     98:1:a7:49:1e:1c   UHLWIi         en1    899
+198.51.100.255     ff:ff:ff:ff:ff:ff  UHLWbI         en0      !
+198.51.196        link#14            UC          vmnet1      !
+198.51.196.1      0:50:56:c0:0:1     UHLWIi         lo0       
+198.51.196.255    ff:ff:ff:ff:ff:ff  UHLWbI      vmnet1      !
+224.0.0/4          link#4             UmCS           en0      !
+224.0.0/4          link#5             UmCSI          en1      !
+224.0.0.251        1:0:5e:0:0:fb      UHmLWI         en0       
+224.0.0.251        1:0:5e:0:0:fb      UHmLWI         en1       
+239.255.255.250    1:0:5e:7f:ff:fa    UHmLWI         en0       
+239.255.255.250    1:0:5e:7f:ff:fa    UHmLWI         en1       
+255.255.255.255/32 link#4             UCS            en0      !
+255.255.255.255    ff:ff:ff:ff:ff:ff  UHLWbI         en0      !
+255.255.255.255/32 link#5             UCSI           en1      !
+EOF
+        want_ipv4_if => "en0",
+    },
+    {   name => "netstat -rn -f inet6 (MacOS)",
+        text => <<EOF,
+Routing tables
+
+Internet6:
+Destination                             Gateway                         Flags         Netif Expire
+default                                 fe80::4262:31ff:fe08:60b3%en0   UGc             en0       
+default                                 fe80::4262:31ff:fe08:60b3%en1   UGcI            en1       
+default                                 fe80::%utun0                    UGcI          utun0       
+default                                 fe80::%utun1                    UGcI          utun1       
+::1                                     ::1                             UHL             lo0       
+2001:db8:450a:e723::/64                 link#4                          UC              en0       
+2001:db8:450a:e723::/64                 link#5                          UCI             en1       
+2001:db8:450a:e723::1                   40:62:31:8:60:b3                UHLWIi          en0       
+2001:db8:450a:e723:208:9bff:feee:d40e   0:8:9b:ee:d4:e                  UHLWI           en0       
+2001:db8:450a:e723:208:9bff:feee:d40f   0:8:9b:ee:d4:f                  UHLWI           en0       
+2001:db8:450a:e723:881:db49:835c:e83e   c8:e0:eb:42:96:eb               UHL             lo0       
+2001:db8:450a:e723:1820:2961:5878:fb72  c8:e0:eb:42:96:eb               UHL             lo0       
+2001:db8:450a:e723:1c99:99e2:21d0:79e6  00:00:00:90:32:8f               UHL             lo0       
+2001:db8:450a:e723:2474:39fd:f5c0:6845  00:00:00:90:32:8f               UHL             lo0       
+2001:db8:450a:e723:808d:d894:e4db:157e  00:00:00:90:32:8f               UHL             lo0       
+2001:db8:450a:e723:9022:cdf6:728c:81cc  c8:e0:eb:42:96:eb               UHL             lo0       
+fdb6:1d86:d9bd:3::/64                   link#4                          UC              en0       
+fdb6:1d86:d9bd:3::/64                   link#5                          UCI             en1       
+fdb6:1d86:d9bd:3::1                     40:62:31:8:60:b3                UHLWI           en0       
+fdb6:1d86:d9bd:3::8076                  00:00:00:90:32:8f               UHL             lo0       
+fdb6:1d86:d9bd:3::85ba                  c8:e0:eb:42:96:eb               UHL             lo0       
+fdb6:1d86:d9bd:3:208:9bff:feee:d40e     0:8:9b:ee:d4:e                  UHLWI           en0       
+fdb6:1d86:d9bd:3:208:9bff:feee:d40f     0:8:9b:ee:d4:f                  UHLWI           en0       
+fdb6:1d86:d9bd:3:837:e1c7:4895:269e     00:00:00:90:32:8f               UHL             lo0       
+fdb6:1d86:d9bd:3:8a5:4e16:4924:ca7d     c8:e0:eb:42:96:eb               UHL             lo0       
+fdb6:1d86:d9bd:3:dbb:dd72:928a:1f4      c8:e0:eb:42:96:eb               UHL             lo0       
+fdb6:1d86:d9bd:3:2474:39fd:f5c0:6845    00:00:00:90:32:8f               UHL             lo0       
+fdb6:1d86:d9bd:3:9022:cdf6:728c:81cc    c8:e0:eb:42:96:eb               UHL             lo0       
+fdb6:1d86:d9bd:3:a0b3:aa4d:9e76:e1ab    00:00:00:90:32:8f               UHL             lo0       
+fe80::%lo0/64                           fe80::1%lo0                     UcI             lo0       
+fe80::1%lo0                             link#1                          UHLI            lo0       
+fe80::%en0/64                           link#4                          UCI             en0       
+fe80::2e:996d:54e6:daa0%en0             70:ea:5a:79:45:4b               UHLWI           en0       
+fe80::208:9bff:feee:d40f%en0            0:8:9b:ee:d4:f                  UHLWI           en0       
+fe80::4ba:362c:664:c432%en0             7c:a1:ae:f:4:f4                 UHLWI           en0       
+fe80::85b:d150:cdd9:3198%en0            00:00:00:90:32:8f               UHLI            lo0       
+fe80::8f2:20e6:a10b:3cdd%en0            70:56:81:ba:5f:37               UHLWI           en0       
+fe80::c20:19a:2ac2:79a1%en0             cc:d2:81:5a:8d:ee               UHLWI           en0       
+fe80::10e4:937a:51ce:a8d9%en0           f0:18:98:29:ef:a3               UHLWI           en0       
+fe80::142a:3ac5:7cb9:2218%en0           90:e1:7b:b9:e5:38               UHLWI           en0       
+fe80::1445:78b9:1d5c:11eb%en0           c8:e0:eb:42:96:eb               UHLWI           en0       
+fe80::1450:3f80:6143:4f7c%en0           b8:e8:56:a3:67:5                UHLWI           en0       
+fe80::18d5:2b64:b66b:88b%en0            e0:33:8e:38:44:3                UHLWI           en0       
+fe80::1c88:3c7:f97b:e538%en0            98:1:a7:49:1e:1c                UHLWIi          en0       
+fe80::4262:31ff:fe08:60b3%en0           40:62:31:8:60:b3                UHLWIir         en0       
+fe80::%en1/64                           link#5                          UCI             en1       
+fe80::2e:996d:54e6:daa0%en1             70:ea:5a:79:45:4b               UHLWI           en1       
+fe80::70:2494:f602:7479%en1             0:61:71:cd:0:10                 UHLWI           en1       
+fe80::4ba:362c:664:c432%en1             7c:a1:ae:f:4:f4                 UHLWI           en1       
+fe80::85b:d150:cdd9:3198%en1            00:00:00:90:32:8f               UHLWI           en1       
+fe80::8f2:20e6:a10b:3cdd%en1            70:56:81:ba:5f:37               UHLWI           en1       
+fe80::c20:19a:2ac2:79a1%en1             cc:d2:81:5a:8d:ee               UHLWI           en1       
+fe80::1445:78b9:1d5c:11eb%en1           c8:e0:eb:42:96:eb               UHLI            lo0       
+fe80::18d5:2b64:b66b:88b%en1            e0:33:8e:38:44:3                UHLWI           en1       
+fe80::1c88:3c7:f97b:e538%en1            98:1:a7:49:1e:1c                UHLWIi          en1       
+fe80::4262:31ff:fe08:60b3%en1           40:62:31:8:60:b3                UHLWIir         en1       
+fe80::%awdl0/64                         link#10                         UCI           awdl0       
+fe80::54df:1aff:fee1:2df5%awdl0         56:df:1a:e1:2d:f5               UHLI            lo0       
+fe80::%llw0/64                          link#11                         UCI            llw0       
+fe80::54df:1aff:fee1:2df5%llw0          56:df:1a:e1:2d:f5               UHLI            lo0       
+fe80::%utun0/64                         fe80::aeea:9fe9:9194:6e66%utun0 UcI           utun0       
+fe80::aeea:9fe9:9194:6e66%utun0         link#12                         UHLI            lo0       
+fe80::%utun1/64                         fe80::583f:da5f:e2bc:4773%utun1 UcI           utun1       
+fe80::583f:da5f:e2bc:4773%utun1         link#13                         UHLI            lo0       
+ff01::%lo0/32                           ::1                             UmCI            lo0       
+ff01::%en0/32                           link#4                          UmCI            en0       
+ff01::%en1/32                           link#5                          UmCI            en1       
+ff01::%awdl0/32                         link#10                         UmCI          awdl0       
+ff01::%llw0/32                          link#11                         UmCI           llw0       
+ff01::%utun0/32                         fe80::aeea:9fe9:9194:6e66%utun0 UmCI          utun0       
+ff01::%utun1/32                         fe80::583f:da5f:e2bc:4773%utun1 UmCI          utun1       
+ff02::%lo0/32                           ::1                             UmCI            lo0       
+ff02::%en0/32                           link#4                          UmCI            en0       
+ff02::%en1/32                           link#5                          UmCI            en1       
+ff02::%awdl0/32                         link#10                         UmCI          awdl0       
+ff02::%llw0/32                          link#11                         UmCI           llw0       
+ff02::%utun0/32                         fe80::aeea:9fe9:9194:6e66%utun0 UmCI          utun0       
+ff02::%utun1/32                         fe80::583f:da5f:e2bc:4773%utun1 UmCI          utun1   
+EOF
+        want_ipv6_if => "en0",
     },
 );