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Secondary dial tone heard on inwards calls from PSTN with T1 CAS MGCP gateway

Core Issue

Cisco IOS  Software based voice gateway runs Media Gateway Control Protocol (MGCP) for VoIP signaling control between the gateway and Cisco CallManager. External callers hear a period of secondary dial tone for inwards calls, specifically Public Switched Telephone Network (PSTN) towards Cisco CallManager. After this burst of dial tone, the call proceeds as expected: the IP phone rings and the external caller hears an in-band ringback.

This is the configuration for the customer's voice gateway router:

!
controller T1 1/0
  framing esf
  linecode b8zs
  ds0-group 1 timeslots 1-24 type e&m-wink-start dtmf dnis
!
!
dial-peer voice 11 pots
  application mgcpapp
  port 3/0:1
!

Resolution

To resolve this issue, perform these steps:

  1. Change the voice gateway router configuration by removing the keywords dtmf  dnis for the ds0-group T1 controller command.

    The new configuration would be as follows:

    ! 
    controller T1 1/0
      framing esf
      linecode b8zs
      ds0-group 1 timeslots 1-24 type e&m-wink-start
    !
    
  2. After the config changes have been made, re-register the gateway to the Cisco CallManager by issuing the no mgcp | mgcp config command.

Version history
Revision #:
1 of 1
Last update:
‎06-22-2009 04:11 PM
Updated by:
 
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