/mcpc=IN IP4 10.0.0.1 t=0 0 m=audio 19054 RTP/AVP 0 c=IN IP4 10.0.0.1 a=rtpmap:0 PCMU/8000 a=silenceSupp:off - - - - ACK sip:2101@10.0.0.1:5060 SIP/2.0 Via: SIP/2.0/UDP 10.0.0.2:5060;branch=z9hG4bK16A56 From: sip:8131101@10.0.0.2;tag=8D66B94-7BF To: sip:2101@10.0.0.1;tag=DD32900-5D4 Date: Fri, 25 Feb 2011 19:23:25 GMT Call-ID: F12F0BBB-403D11E0-81869D5B-499FBE40@10.0.0.1 Max-Forwards: 70 CSeq: 101 ACK Allow-Events: telephone-event Content-Length: 0 Symptom 1: CUBE Rejects ReINVITE with 488 If you encounter this problem, complete these steps: Enable debugs and collect for a test call. 1. Verify that T.38 or Fax Pass-Through is configured globally. 2. If T.38 or Fax Pass-Through is not configured globally, ensure that T.38 or Fax Pass- Through is configured under both the incoming and outgoing dial-peers based on the Call Control Application Programming Interface (CCAPI) debugs. 3. If the problem is still not resolved, enable debug ccsip all (in a logging buffer with logging buffered 5000000 debug) in order to determine why SIP rejects this ReINVITE. 4. Symptom 2: CUBE Rejects RequestMode with RequestModeReject If you encounter this problem, complete these steps: Enable debugs and collect for a test call. 1. Verify that T.38 or Fax Pass-Through is configured globally. 2. If T.38 or Fax Pass-Through is not configured globally, ensure that T.38 or Fax Pass- Through is configured under both the incoming and outgoing dial-peers based on the CCAPI debugs. 3. If the problem is still not resolved, enable debug h225 events, debug h225 q931, and debug h245 events in order to determine why H323 rejects this RequestMode. 4. Vendor Specific Information Verizon The Cisco Technical Assistance Center (TAC) has noticed that, although Verizon claims support for T.38 over SIP, they never initiate a switchover from a voice call to T.38 when they operate at the TGW. G This is a known limitation in their environment, and it does not appear that they are going to fix it. G When the OGW is a FoIP server, you can usually set the server to initiate a switchover even G