Core Issue
Currently, it is not possible to connect a fax machine to an Analog Telephone Adaptor (ATA) that is connected to Cisco CallManager Express through Skinny Client Control Protocol (SCCP). Fax passthrough on Cisco CallManager Express or ATA skinny code has not been tested and is not a supported solution.
The feature request for this functionality is being tracked by Cisco bug ID CSCed47764: Call Manager Express does not allow for fax passthrough configuration.
Resolution
T.38 and Cisco Fax Relay support fax passthrough in an ATA or Cisco CallManager Express environment. To accomplish this, choose from one of these options:
- Connect the fax machine to an ATA running H.323 mode. To learn how to configure ATA in H323 mode, refer to Configuring and Troubleshooting an ATA 186 with a Cisco IOS Gateway.
- Connect the fax machine directly to the Foreign Exchange Station (FXS) port of a Cisco CallManager Express router for fax support from the Cisco IOS Software gateway code.
Note: The ATA only supports fax passthrough. To configure ATA for fax passthrough, refer to Configuring and Troubleshooting the Cisco ATA 186 with Fax.
For information on fax protocol support for various VoIP gateways, refer to the Fax Support Matrix section of Cisco AVVID Gateway Support for Fax Relay and Fax Passthrough.
