CUCM external calls appear connected, but never show connected on call

[MartinBLack54823]

Place an external call from Voip phone 19xxxxxxxxxx, phone does not ring but shows it is on a call, with on call options appearing on soft keys, hold, end call, transfer. person being called never receives call. Internal calls to extensions are fine. can receive external calls no problem.

[Stephanie Knoop]

It sounds as if you might have a firewall issue to resolve. It seems that the signaling may not be getting through. You might want to check firewall rules for your signaling protocols or check to see that that SIP Inspection is disabled.

Verify which signaling protocols you are using and ensure they are open in the appropriate firewalls:

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/12_0_1/systemConfig/cucm_b_system-configuration-guide-1201/cucm_b_system-configuration-guide-1201_chapter_01010110.html

Great article in SIP Inspection and VoIp.

https://getvoip.com/blog/2020/09/01/what-is-sip-alg/

[MartinBLack54823 · Accepted solution]

ISP finally acknowledged issue was on their end, but were not forthcoming in what the resolution was. I suspect the traffic was not handled as voice traffic.