First, thank you very much for ZBXNEXT-8721 and ZBXNEXT-5401 .

This issue is to let you know, that both net.dns.get's query_time and net.dns.perf report a zero query time for NXDOMAIN results.

I hope this missing bit could be added/fixed. Ability to monitor performance of the negative case is important especially for the PTR queries, which openssh does by default on every login.

I also believe that net.dns.perf should return an error when the value is not available.