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User finds it difficult to configure fax relay between a Cisco 6624 skinny or MGCP gateway and an H.323 Cisco IOS gateway

Core Issue

When configuring fax relay between a 6624 gateway and an Cisco IOS  H.323 gateway, problems may arise due to a mismatch between the two fax modes the gateways are running. In order for the fax to be successful, the two gateways must negotiate the same fax mode. By default, a Cisco router and gateway uses fax-relay negotiation. However, as from the 3.010 load for WS-X6624 (A002A3A0), the default fax mode is fax pass-through.

Resolution

Ensure that the fax mode matches between the gateways. In particular, if you leave the CallRestartTimer with the default setting of 5000 ms, the 6624 port uses fax pass-through. To use fax relay, change this value to 1235. The other option is to use fax pass-through on the H323 gateway.

For the Cisco CallManager configuration, perform these steps:

  1. Open up the Cisco CallManager Administration panel.
  2. Click the 24 port Foreign Exchange Station (FXS) blade configured on your Cisco CallManager.
  3. Select the port you are using (port to which your fax has been connected).
  4. Set the CallRestartTimer to 1235 ms. Click Update.

        Note: This procedure only applies to skinny gateways, not to H.323 gateways.

If you leave the CallRestartTimer with the default setting of 5000 ms, the port uses fax pass-through. If that is the case, make sure to also use fax pass-through on the H.323 gateway.

To configure the H.323 gateway fax relay, set the fax-rate command to 9600 or 14400 baud in cases where the default G.729 codec is being used, as shown. When using G.711, this command is not required.

dial-peer voice 2 voip
 destination-pattern 2000
 session target ipv4:10.200.72.37
  fax-relay ecm disable
  fax-rate 9600

!

dial-peer voice 3 pots destination-pattern 0T direct-inward-dial port 1/0:15

To configure the H.323 gateway for fax pass-through, issue the fax rate disable command on the voip dial peer, as shown:

dial-peer vo
ice 2 voip
 destination-pattern 2000
 session target ipv4:10.200.72.37
  fax-relay ecm disable
  fax rate disable
  no vad
!
dial-peer voice 3 pots
 destination-pattern 0T
 direct-inward-dial
 port 1/0:15

For more information about configuring faxes, refer to Fax configuration on a Cisco WS-X6624 Using an H.323 Gateway.

Voice Gateways

IOS gateways

Non-IOS gateways

Version history
Revision #:
1 of 1
Last update:
‎06-22-2009 04:47 PM
Updated by: