diff --git a/Dockerfile b/Dockerfile
index 193d0ab..9672abc 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -24,6 +24,7 @@ RUN install -dm 2750 -o root -g root /var/lib/monit
 COPY --from=build /etc/monitrc /etc/monitrc
 COPY ./nsupdate.sh /usr/local/bin/nsupdate
 COPY ./whatsmyip6.sh /usr/local/bin/whatsmyip6
+COPY ./whatsmydefaulteth.sh /usr/local/bin/whatsmydefaulteth
 COPY ./syslogize.sh /usr/local/bin/syslogize
 COPY ./zeroconf.sh /usr/local/bin/zeroconf
 COPY ./zeroconf.conf /etc/zeroconf.conf
diff --git a/whatsmydefaulteth.sh b/whatsmydefaulteth.sh
new file mode 100755
index 0000000..c5f8225
--- /dev/null
+++ b/whatsmydefaulteth.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+ip -6 r | grep default | tr -s " " | cut -d " " -f 5
diff --git a/whatsmyip6.sh b/whatsmyip6.sh
index 641fb7d..858a559 100755
--- a/whatsmyip6.sh
+++ b/whatsmyip6.sh
@@ -1,3 +1,3 @@
 #!/bin/sh
 
-ip address show ${1:-eth0} | grep inet6 | grep global | tr -s " "  | cut -d " " -f 3 | cut -d / -f 1
+ip address show ${1:-$(whatsmydefaulteth)} | grep inet6 | grep global | tr -s " "  | cut -d " " -f 3 | cut -d / -f 1