Have had a UC520 in the field at my office for 10+ years, running 12.4(11r)XW3. ATT has been providing their SIP connection via fiber and a Cisco router to UC, with the UC hitting a remote SIP server, and things have been working great. They wish to upgrade to a 50 meg circuit, using their own proprietary router that also acts as the SIP server - and there-in lies the problem.
Using the test DNs our system can make calls, but when calls are initiated to the system it gives the "Error 488 Not Acceptable Media" error to ATT. We tried some basic things of removing codecs from the config, etc. but no luck.
Can anybody provide some suggestions, especially as it would pertain to ATT?
Thank you.
