CUBE not responding to 401 messages

[amohod]

we have CUBE which is directly connected to the internet and it is configured with SIP trunk. The SIP trunk was working fine till yesterday but all sudden SIP trunk got unregistered. When we check the logs and had troubleshooting session with TISP, we observed that CUBE is sending a register message and TISP responding back with 401. But on our side, we do not see the 401 messages in CUBE sip logs. When we turn on packet capture on the router interface, those packets show up in packet capture. 

It looks like some process in CUBE is discarding 401 packets coming from TISP. As CUBE is not responding to 401 requests from TISP and not sharing credentials with TISP, the SIP trunk is not getting registered.

Kindly guide us on how to fix the issue.

Thanks in advance

[Vaijanath Sonvane]

Hi,

• What model of ISR you are using and what is the version?
• Is there any change made on your side? 
• Are the SIP Trunk credentials changed on ITSP side? Was there password expiration set on ITSP side?
• Have you turned on the logging on your CUBE router? Post the logs for debug ccsip messages command. 

As as add-on, I do see few software bugs related to similar issue. It may be worth to check if workaround in the software bug can resolve your issue.

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCui97039

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCtt43848

[amohod]

Here is my reply

• What model of ISR you are using and what is the version?- ISR 4331, IOS XE 03.13.04.S 
• Is there any change made on your side? there were changes in interface connecting to LAN....nothing on WAN side
• Are the SIP Trunk credentials changed on ITSP side? Was there password expiration set on ITSP side? We reset the password but still issue is same
• Have you turned on the logging on your CUBE router? Post the logs for debug ccsip messages command. For security reasons, I will not able to share the debug messages. But I can assure you that we checked the logs on both sides. As explained earlier, TISP logs show 401 messages sent to CUBE and packet capture on our CUBE confirms that it has received the 401 messages. But for some reason, that message does not show up in SIP debug. In CUBE we just see multiple Register messages sent to TSIP but no message from TISP.

[amohod]

I think we found out the issue. We are hitting with bug CSCuy82008. When I remove the NAT configuration on WAN interface, the SIP trunk register. We are planning to move the NAT on another interface.