Traefik Dashboard Working but only listening on IPv6

TheFutonEng

Greetings friends! Starting this post off by saying I answered my own question while typing it up. Decided to still post it in case someone else was scratching their head for the same reason.

In lab 10.1, the traefik ingress controller was successfully deployed and the dashboard is reachable against port 8080 on both of the worker nodes which, groovy. What wasn't clear is how IPv4 connections were working when both nodes only showed that they were listening for incoming connections on 8080 via IPv6:

`[user@cka-node01]$ netstat -tan | grep LISTEN | grep 8080
tcp6 0 0 :::8080 :::* LISTEN
[user@cka-node01]$

[user@cka-node02]$ netstat -tan | grep LISTEN | grep 8080
tcp6 0 0 :::8080 :::* LISTEN
[user@cka-node02]$`

Yet, IPv4 connections were working just fine:

[user@cka-node02]$ curl -s -o /dev/null -w "%{http_code}\n" http://127.0.0.1:8080/dashboard/ 200 [user@cka-node02]$

What allows this to happen is sysctl variable net.ipv6.bindv6only. In short, if it is set to zero, it will allow both IPv4 and IPv6 connections. If set to 1, it will only allow IPv6 connections.

[user@cka-node02]$ sysctl net.ipv6.bindv6only net.ipv6.bindv6only = 0 [user@cka-node02]$

Hope this helps out someone.