/mcphappens. The T.30 specification is also very helpful. For the protocol analyzers, decoding can be difficult because sometimes the encodings are proprietary, or the analyzer software does not have the specific decode needed. For fax relay that uses VoFR and VoATM, Cisco gateways use standards-based Annex D from the FRF11 specification. If the protocol analyzer is not able to decode the frame, the frame can be manually decoded with this specification. With fax relay and VoIP, a Cisco proprietary format is used for the fax relay packets. With fax analyzer and protocol analyzer information, you are able to resolve fax relay problems. Few fax relay problems reach this point, and when they do, escalation and DE resources must be involved for further assistance. In addition, provide all other information relevant to the problem. Open a TAC Case If this document has not enabled you to isolate and resolve the problem, open a case with the Cisco Technical Assistance Center (TAC) and provide this information: Network topology description (PDF, Visio, or Microsoft PowerPoint format). • The fax machines used, which include vendor and model information. • The history of the problem. Useful information includes whether the implementation is new or an established network that worked well and then failed. If the network was established, what changed before the problem occurred? Is the problem intermittent? Can the problem be reproduced, and, if so, what are the steps needed to reproduce the problem? • Output of the show tech command from both fax gateways and all the routers on the IP path, and relevant information for the active non-Cisco network equipment. • A pair of the call traces with these debug flags enabled: debug voip ccapi inout ○ debug vtsp all ○ debug isdn q931 (if the ISDN or Q.Sig is involved) ○ • A pair of the show voice call and show voice dsp outputs. • A pair of the fax analyzer traces connected in the monitor mode to the origination and termination fax machines, if available. • Results of the troubleshooting and debugs performed, if available. • Related Information originally published to https://www.cisco.com/c/en/us/support/docs/voice/fax-modem-over-ip/20227- faxrelay-tsguide.html original MDF tag is: Technologies:Voice:Fax / Modem over IP. Document ID is 20227