I stumbled into an interesting issue today that gave me a smile when I determined it was a DNS issue.
I was doing some consulting work around WireGuard for a client, and noticed a number of odd issues and just general wonky behavior with everything being slow. This specific client uses Ubuntu Linux while I’m more of a RedHat/CentOS/Rocky guy so I thought it was an issue with the DNS caching that Ubuntu utilizes in systemd-resolve. A few quick tests using a Windows client proved that the issues weren’t limited to just the Ubuntu server, it was impacting every device. DNS queries were taking between 5 to 6 seconds and some were timing out entirely.
The client had mentioned some oddities and issues and I thought there might be a duplicate IP on the network – pretty standard affair in some networks. This wasn’t a duplicate IP issue so I went straight to the DNS servers themselves – Microsoft Windows Server 2019. I found that the root forwarders for each server were setup to use some very old Verizon DNS servers – and wouldn’t you know that some of them were no longer responding. I removed all the Verizon entries and added the two standard Google DNS servers – 22.214.171.124, 126.96.36.199. After applying that and restarting each DNS server the problem was gone and everything was running smoothly again.
What do you use for your DNS forwarders? Or do you rely on the root hints file maintained by Internic?