Does resolver fallback to next nameserver if it can't query the result?

[voronond]

I know that we provide multiple nameservers, the library queries one-by-one from top of the list in case that DNS server is unreachable. But in a case that the first DNS does not have an answer and the second does, resolver immediately raises an exception NXDOMAIN/NoAnswer. On the other hand, system resolver should fallback to the next on (after calling gethostbyaddr for example).

Is this intended behaviour or am I mistaken and system resolver does not do that?

Thanks!

[bwelling]

That is not how the system resolver works. NoAnswer is always a final answer. NXDOMAIN may indicate that other entries in the search list should be tried, but will not try other name servers.

[voronond]

Thank you for the explanation.