I stumbled across an issue with Cisco’s “NAT Support for SIP” feature today. Some very long SIP invites (actually spanning two packets as a SIP continuation) were being truncated. The 1420 byte initial packet was losing 15 bytes, the 72 byte continuation was unaffected. A “debug ip nat sip” showed the error:
IPNAT SIP SDP: End of line beyond end of buffer.
It doesn’t seem this buffer can be tuned so this behaviour appears to be buggy. Nothing on the Cisco bug toolkit so I’ve raised a TAC request.