/mcpthere could be a fax relay bug in the Cisco IOS Software release installed. For example, if a fax relay that uses VoFR does not work in Cisco IOS Software Release 12.1(2)T, you can search for bugs with the Bug Toolkit on CCO. In this example, use these values: Major Version: 12.1 ○ Revision: 2 ○ Feature/component: VoFR ○ Keyword: fax ○ One of the bugs is Cisco bug ID CSCdr65984 (registered customers only) , entitled "fax doesnt work for vofr." This bug caused all fax relay to fail for VoFR, and an upgrade is needed to a Cisco IOS Software release in which this bug is no longer present. Eliminate hardware faults. In some cases, it is easier to isolate the problem if you exclude potential problem sources, one by one. Replace different hardware parts and use alternative IP connections between the gateways. When extra hardware is available, these steps can help: Use different ports on the routers. If your configuration involves two gateways connected to the PBXs or PSTN with E1 or T1 and if you have the FXS ports available, try to connect the fax machines directly to the FXS ports on the voice gateways. This procedure helps further isolate the problem when the possibility of the E1-card failure, problems on the telephony side, or E1 synchronization or cable problems are excluded. ○ Try different hardware. If you have another voice gateway with FXS ports available to you, try to connect it directly with the Ethernet crossover cable to each of the voice gateways and send a fax with the fax machine connected to the FXS port. This procedure helps determine if there are problems in the VoX network such as queuing, fragmentation, or prioritization. ○ • Use debug commands on the router to determine the problem. See the "Debugging" section for details about debug commands useful for troubleshooting fax relay problems. • Debugging T.30 Messages The debugs can be difficult to understand if you are not familiar with the messaging that occurs within a typical fax transmission. This is a graphical representation of the basic T.30 transactions that occur for a single page fax transmission.