/mcpThis debug shows the T.30 events that take place in the DSP within fax relay. It is important to remember that the debugs that take place from the perspective of the DSP interact with the fax device, so any "Fr- MSG-TX" or transmit message is transmitted from the DSP to the connected fax device. Any message that the DSP says that it detects, or "fr-msg-det" message, is a message that it received from the connected fax device. This graphic illustrates the directional flow of the DSP messages when the debug fax relay t30 all command is issued. From the failed fax transaction in the debug, you can see several "bad crc" messages followed by a Failure To Train (FTT) message from the far side. From the debugs, it looks as if the problem involves the training signal. The bad crc errors and the FTT (Failure To Train) message returned from the other side indicate that the signal is corrupted or incompatible with the Cisco fax relay protocol. This debug is taken from a fax relay problem that occurs with a Lexmark Optra fax machine. The Lexmark is V.34 capable and attempts to connect at V.34 rates. V.34 is not supported in Cisco fax relay, and training errors occur. See Cisco bug ID CSCdv89496 (registered customers only) for more details. The Working Examples of T.30 Debugs page provides more information about how to read these debugs and an example of a successful debug and ECM mode fax analyzer trace. Debug vtsp all There are also other debug commands that can be useful to troubleshoot fax relay problems. These debugs are not as easy to read or provide as much information as the T.30 debugs, but they can still be useful. Voice Telephony Service Provider (VTSP) is an architecture that defines the interface between the Cisco IOS call control and a DSP end point connected to standard telephony equipment such as a PBX, fax, or central office through analog or digital interfaces. For VoIP T.38 or fax relay, debug vtsp all can provide useful state information from the router. As discussed in of the troubleshooting section, this debug command can be used to determine if the fax codec