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External calls fail through the gateway router on Cisco CallManager - user hears the reorder (or fast busy) tone

Core Issue

Cisco CallManager may be configured to use 9 to allow outside access via a gateway router. The Cisco CallManager route pattern is configured as 9.@ to direct these calls out an H.323 gateway with the ISDN PRI interface to the public switched telephone network (PSTN). The caller is unable to dial local numbers that begin with 9.  When 9,9021234 is dialed, the only digits that make it to the gateway are 021234. 

The Cisco CallMananger and/or the gateway router may be configured to strip off leading access digits that the user dials when making an external call through an H.323 gateway. If the access code is left on the digit string sent to the local exchange, the call may fail and the user hears a reorder (or fast busy) tone. Also, if extra leading digits are stripped off, the call likewise fails.

If the gateway router is connected to a PBX, the leading access digit may need to be retained, or even changed to allow outside access through the PBX to the PSTN.

Resolution

The Cisco CallManager is configured with a route pattern of 9.@ to direct calls to the H323 gateway.

Under the Called Party Transforms section of the Route Pattern Configuration screen, there is an option for 'discard digits.' If the pre-dot option is set, the leading 9 access code is removed from the called party string that is sent to the H.323 gateway.

The gateway has a plain old telephone service (POTS) dial peer similar to the following:

!

dial-peer voice 1 pots

destination-pattern 9

port 1/0:23

!

For any calls where the user dials a 9 access code, then a local number starting with 9, the Cisco CallManager removes the 9 access code and sends the call to the gateway. The above dial peer then strips off the next 9 (first digit of local number), so if the intended number to be called is 9,9021234, the actual digits sent to the telephone network are 021234.

The solution is to set the Called Party Transforms Discard Digits option to . The leading 9 access code is included in the called number that is sent to the H.323 gateway, which matches on the POTS dial peer. The 9 access code is stripped off by the POTS dial peer (explicitly matched digits are removed by default on POTS dial peers) and any subsequent digits in the called number are sent to the telephone network.

See also Gateway Issues

CallManager Versions

CallManager 3.x

CallManager 4.x

Voice Gateways

IOS gateways

Version history
Revision #:
1 of 1
Last update:
‎06-17-2009 10:13 PM
Updated by: