Are you using MGCP or H.323 on the with CM and GW ?

If H.323, the answer has been given above. If using MGCP, you have two choices:

1. On the GW, configure and pots dial-peer as for answer above. Also configure a voicep DP with "incoming destination-number XX", "codec g711u" and "no fad". This is the simple solution. Configure an H.323 or SIP endpoint on the CCM with number.

2. On the GW, configure the FXS port in SCCP mode:

http://cisco.com/en/US/products/ps6441/products_feature_guide09186a0080483a76.html

Then register this post as it was just a phone under CM. This is more complicated, I think,

Hope this helps, please rate post if it does!

Depending on whether you are using MGCP or H323, one other important consideration is the transformation for how the DID is routed.

For example it will be necessary to configure translation rules within either CCM or on the gateway for H323 in order to matched the dialled digits are route the call accordingly.

If you have a seven digit dial-plan and your extensions are 5581200 to 5581299 then it would not be necessary to configure transformations for either MGCP or H323.

As mentioned in a previous post for H323 the destination-pattern for 5581250 on the POTs DP is all that is required. With MGCP you only need to ensure that the gateway endpoint in CCM is configured for ALL or 7 significant digits and the partition assigned to you DNs is within the endpoint CSS.

Regards

Allan.