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Hookflash transfers from the CVP to the H.323 IOS gateway results in disconnected calls

Core Issue

This is the call flow/setup affected:

PBX ---> FXO-loopstart ---> GW ---> H.323 ---> GK ---> CVP

The Cisco Customer Voice Portal (CVP) performs a hookflash transfer, and two seconds later disconnects the call. The H.323 gateway receives the hookflash and starts to relay the digits out one by one. During this process, the gateway receives the Close Logical Connection from the CVP, and then a Disengage Request from the gatekeeper to close the IP leg. This request does not allow the gateway to relay the remaining digits in the hookflash transfer. This results in call failure since there are missing digits.


There are three ways to workaround the CVP hookflash transfer issue:

  1. Add additional commas to the end of the ICM (hookflash) label after the digits in order to introduce a delay.

  2. On the CVP Voice Browser machine:
    1. Regedit.

    2. Add this entry: SOFTWARE/Cisco Systems,Inc./ISN/Customer/Voice Browser/Dynamic/HookflashHangupTimeout

    3. Make it REG_DWORD and set it to the number of milliseconds for the CVP to wait before the call is disconnected after the digits are sent.

      The default is 2000, which could be too short in some cases.

    4. VB does not need to be restarted for this to take effect.

  3. Check the digit duration value on the voice-port config on the Public Switched Telephone Network (PSTN) gateway (GW).

    The default is normally 100ms. This can be reduced to as low as 50 ms. Make sure the PBX/PSTN switch can recognize it.
Version history
Revision #:
1 of 1
Last update:
‎06-22-2009 04:04 PM
Updated by: