CUCM - slow SNMP response traced to DNS IPv6 query?

[Randall White]

I have been having intermittent problems with Emergency Responder and Informacast failing to sync to CUCM and import new phones. The problem was traced to slow SNMP response to certain O.I.D.s, like  1.3.6.1.4.1.9.9.156.1.1.2.1.7 (ccmInetAddress), by the CUCM nodes.

I ran a packet capture, and I can see that every time CUCM receives this request, it sends out a DNS Type AAAA query to resolve it's own hostname. It does this multiple times for each SNMP request. Sometimes DNS is slow or times out, this seems to be causing the SNMP problem. I don't run IPv6 and I thought it was disabled on CUCM.

Is there any way to completely disable IPv6?

Why exactly does CUCM need to resolve it's hostname for an SNMP request?

This is CUCM version 10.5.2.10000-5

Thanks, Randy

[Aeby Vinod]

the behavior is mentioned on the following bug.

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCtb70375

As for why the AAAA record query instead of the A one, can you attach the pcap on this post.

Please rate if you find this helpful.

Regards,
Aeby

[Randall White]

Thanks, I will open a TAC case. According to CSCtk05934 bug it is not possible to completely disable IPv6 on Voice OS products.