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New Member

Need help with Fax relay for ccm 4.1 mgcp and 3825 fxs port

Hi Everyone,

I have a 3825 Router with CallManager 4.13 with MGCP.

I'm having an issue with my 1 fax machine. I can receive fax, but cannot sent out fax. Getting fast busy. It feels like it is a route pattern issue, but I cannot figure it out. I have a default 9.@ pattern. The fax machine is connected to an fxs port 0/0/0. I have a translation pattern with 777 to go to this fax machine port vie H.323 gatway pointing to the router itself. From the fax machine, I can call internal numbers without any issue, just external numbers that it is having issue. I've also tried using the T.38 fax relay, but it only address receiving fax, not sending.

This article:

Also, I've looked at this below document for MGCP.

Neither of these seems to fix my issue. Please help, or if anyone can suggest a working solution with similar scenario, that would be great. Thanks

New Member

Re: Need help with Fax relay for ccm 4.1 mgcp and 3825 fxs port

Cisco IOS Software Release 12.2(11)T2 makes the mgcp fax t38 gateway force command available. This provides a way to enable gateway controlled T.38 fax relay between a MGCP gateway and another gateway, even if the capability to use T.38 and Named Signaling Events (NSEs) cannot be negotiated by the MGCP call agent at call setup time. For more information on this command, refer to Update to mgcp fax t38 Command.

Unfortunately, this command is not available on the MRP since the Cisco IOS T-train is not supported. Therefore, make use of T.38 by putting this configuration on the MRP:

voice service voip

fax protocol t38 ls-redundancy 0 hs-redundancy 0

h323 call start fast This configuration forces the fax relay to use T.38 standards. However, it requires the use of H.323 rather than MGCP.

If you want to continue using MGCP, Cisco proprietary fax relay is required and works fine for Cisco CallManager and Cisco gateways.

Note: The mgcp fax t38 inhibit command is required for operation with Cisco CallManager version 3.1.2c, but is optional for version 3.1.3a and later. This command prevents the MRP or Analog Station Interface (ASI) from sending T.38 fax gateway information to the Cisco CallManager. This command is also required for Cisco Base Transceiver Station (BTS) 10200 versions earlier than 3.0.

For more information on resolving fax relay, refer to Fax Relay Troubleshooting Guide.

Cisco AVVID Gateway Support for Fax Relay and Fax Pass-Through


Re: Need help with Fax relay for ccm 4.1 mgcp and 3825 fxs port

Can you post the actual router configuration minus passwords, etc.

Thank you,