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On the H.323 IOS gateway, no busy tone is heard on the IP phone if the dialed PSTN number is engaged. The IP phone receives a reorder tone after a period of silence

Core Issue

This problem is seen even when the correct source IP address is bound to the correct IP interface on the H.323 gateway, with the voice rtp send-recv command configured.

In this case, the debug isdn q931 command shows that the network is clearing the call correctly with the user-busy cause.


In order to resolve this issue, add the voice call convert-discpi-to-prog command to the global configuration of the H.323 gateway. This command converts an inbound ISDN disconnect message with a PI to an H.225 progress message with the same PI value.

Refer to Troubleshooting No Busy Tone and No Announcement Messages on ISDN-VoIP (H.323) Calls for further details.

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