I have a customer with a CUCM 7.1(5), with a SIP trunk connected to a third party dialer. The local users login to the dialer application via the web and the third party IP PBX calls their IP Phone Via the SIP Trunk. This was working fine until the customer firewall recently went out. I can observe attempted calls hitting the CUCM however the calls fail. Attached is a part of a trace that I captured, this appears after every attempt. I have verified that the extension referred to (which is an SCCP IP Phone) is valid and I have checked CSS's. Does anyone have any other Ideas? Thanks!