We are a small organization running some 25 websites on a Plesk VPS at rtvps.nl. The DNS for these domains runs on the Plesk service as well. Some of the domains hosted on this server include roads-technology.nl and jouwteambuilders.nl.
This all works fine most of the time. Once in a while though the DNS server stops responding causing the websites to become unavailable. This typically happens once a week or so and lasts anywhere between 4 and 8 hours. After that the DNS server comes back online and works correctly like before.
So far I tried looking in the configuration but could not find anything out of the ordinary. I also tried to find reports of anyone who experienced the same problem without much success. I tried running named as a foreground task with debugging information enabled but I’m afraid my DNS knowledge is insufficient to properly interpret that information. Even when the DNS server is unresponsive I do however still see numerous requests coming in, typically a couple per second.
During the failure it seems that the DNS server is still running but for some reason no longer replies to requests. When I login with SSH on the server the results vary. Sometimes the nslookup command seems to work fine on the server, sometimes I get a timeout, sometimes a server failure. When I manually enter the IP address for one of the domain in the hosts file (Windows) the site loads normally so I think I can rule out other server problems.
The server runs on Ubuntu 20.04.6 LTS with Plesk Obsidian 18.0.73 Update #3 Web Host Edition and BIND 9.18.30.
Please keep in mind I’m not an expert on the DNS system so feel free to ask for additional information.
