It's always DNS, or the idiot that set it up
Reading time: 2 minutes (365 words)Author: @pugmiester
Tags: dns , ipv6
Today’s random “It’s always DNS” message is brought to you by the idiot that didn’t configure it properly.
On my quest to do more IPv6 stuff to learn about it, I’ve had GUA IPv6 addresses on all my home servers for a while but I’ve been using them now and then. With our new ISP and fixed addresses I’ve been using them more. In a recent post titled A Short IPv6 Guide for Home IPv4 Admins it mentions about not picking IP addresses for your devices and just let them figure one out for themselves and use DNS. I’ve been setting manual addresses on my devices so I could remember where they are but if DNS is working anyway, I shouldn’t care, so I started just using the machine selected addresses instead.
I adjusted the settings on 2 servers on Monday and they seemed to be happy so I made the same changes for another host last night but couldn’t get it to work. I thought I had broken things when neither my phone or laptop could ping “server3.lan”. I was obviously missing something so I put the IP in manually and it worked.
Thinking I’ve broken something, I put the IP back for now and figured I would check again tomorrow with fresh eyes.
Tomorrow arrives and the problem is still here. What the heck is going on? Even sitting on the DNS server itself, it’s not able to resolve the name. I’ve obviously screwed something up, but what? And then I saw it, while looking at the web interface on my pihole box I noticed my mistake.
I’d previously been setting 2 DNS entries for each host to the effect of “server3-6.lan” (IPv6) and “server3.lan” (legacy IP). I’ve been replacing these with “server3.lan” (IPv6) and “server3.legacy.lan” (legacy IP) but I had completely forgotten to update the names so I still had “server3-6.lan” pointing to the IPv6 address. I updated the DNS records properly and hay presto, I can ping “server3.lan” using IPv6 as I should be able to.
It’s now fixed and working as expected. Sometimes you just need to take a break and look at things the next day with fresh eyes.