Solved: UC 15 - Reverse DNS failing

Clifford McGlamry · ‎03-04-2025

Dealing with a strange issue here. In my lab, I have a pair of Microsoft DNS servers configured with Reverse DNS zones. Servers built with earlier UC versions work just fine, and have no complaints about forward or reverse DNS. But anything built with v15 (CUCM and CUC have been tested) squawk that reverse DNS is failing.

The DNS servers are reachable. I can manually resolve both A and PTR records with no issue. But for some reason, v15 complains continuously about failed reverse DNS.

Has anyone else run across this and figured out why it's happening?

Clifford McGlamry · ‎03-04-2025

Put a wireshark on the DNS server, and I see what is happening.

For some reason, in version 15, the DNS query is adding OPT onto the end of the query, and my DNS server doens't know what to do with this. The script apparently doesn't know how to send it without sending that. See wireshark capture attached.

View solution in original post

Clifford McGlamry · ‎03-04-2025

Put a wireshark on the DNS server, and I see what is happening.

For some reason, in version 15, the DNS query is adding OPT onto the end of the query, and my DNS server doens't know what to do with this. The script apparently doesn't know how to send it without sending that. See wireshark capture attached.

Clifford McGlamry · ‎03-04-2025

Hitting ignore on the installer allows it to continue, and it works okay in my lab. Not really any way for me to report this to Cisco as a bug without a customer instance.