Too much Server failure

[marcelsch71]

Hello, I woluld like to ask you for help
I have a Technitium dns server configured with five VLANs and I use it as a root server. My question is when a PC on VLAN 10 makes a DNS request and Technitium doesn't know the answer and has to ask the some root DNS server on the Internet, from which interface will the request go to the Internet? Will it use the gateway from the given VLAN 10 or will it use the default gateway of the Technitium DNS server? Why am I asking: I have a lot of errors on Technitium and I have to refresh some pages several times before they load. I still need to fine-tune the settings on the Opnsense firewall. Many thanks for explanation

[ShreyasZare]

Thanks for the post. The outbound requests will go from the interface which has the default route on the server. Server Failure responses are generic and mean that the DNS server could not find an answer before the request timed out. Reason for this can be anything so you need to check for error logs in the Logs > View Logs section on the admin panel. The error description will tell you what went wrong. You can share the error logs here if you need help understanding them.

When you run a recursive resolver, it is expected that the resolution may take a while when the DNS cache is empty. This will cause the DNS server to return server failure responses. Once the DNS server is running for a day or two and the cache builds up, you will see this issue reduce significantly.

[marcelsch71]

Thanks a lot for the answer and explanations. I have attached some log parts with resolution failure. Please what do you think about that?
Technitium log.txt

[ShreyasZare]

These are just "Connection timed out" errors which means that the name servers for the domain names did not respond in time. Its pretty common thing when running recursive resolver since this depends on network conditions between you and the name servers. If the name servers are geographically far away or there are some network issues in between then such delays in response may occur. The domain names should work after a few more retries.

[marcelsch71]

Thank you for the diagnosis. I noticed that there are many dns servers in the root zone. But only a few of them are used. How does the Technitium dns server determine which one to connect to?
Technitium dns server is an amazing software. Great job.

[ShreyasZare]

Thanks for the compliments. The DNS server uses machine learning algorithm to sort the available name servers and then uses them in that order. But it will use all name servers and only sort them as per the algorithm to use them.