I am facing a strange problem with CIsco UC 500. Most calls from the provider are successful, except for some specific calls.
The UC 500 receives the Invite but then responds with message 500 (internal server error).
I have attached the SIP trace. The UC is at 172.21.16.77 and the provider's network is 192.168.1.0/24.
The proxy is in the ACL of the voice source group.
Doing an external tcpdump I noticed that for the failed calls the proxy is sending the SIP Invite in an IP fragment and immedately the UC is generating the Internal error message. Any ideas?