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Conference calls between an IP phone and PSTN are dropped after 10 minutes or more in Cisco routers running Cisco IOS Software Release 12.2(13)T with NM-HDV when the user configures a hardware conference bridge on a Cisco CallManager with DSP


Core Issue

This symptom is observed on a Cisco 2600 series router that runs Cisco IOS  Software Release 12.2(13)T and Cisco CallManager version 3.1.4b. The symptom may occur on Cisco routers that have the ability to perform hardware conferencing by using the High Density Voice Network Module (NM-HDV). The symptom does not depend on the Cisco CallManager version. However, the user must configure the Cisco CallManager to use the Digital Signal Processor (DSP) resources on the Cisco router. The user must configure a hardware conference bridge on the Cisco CallManager.


To temporarily overcome this problem, increase the default timer for checking idle RTP streams to prevent the party in the conference from becoming disconnected prematurely. Issue the dspfarm rtp timeout global configuration command.

For a permanent solution, upgrade the Cisco IOS version to 12.3(5)T or later.

To download the required Cisco IOS version, refer to Cisco IOS Software.

This problem is also tracked in Cisco bug ID CSCea47282.

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