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Cisco Bug: CSCtb32339 - CUCM SIP stack is not sending 491 Request Pending to dialogue originator

Last Modified

Feb 07, 2017

Products (1)

  • Cisco Unified Communications Manager (CallManager)

Known Affected Releases


Description (partial)


Rare condition where CUCM SIP stack will encounter a Glare condition due to timing and not send the 491 Request Pending message back to the INVITE originator.  As a result, the originator is not aware of the 491 message and there fore cannot set its retransmission timer appropriately as per spec.  This results in a "stuck" state for the dialog and the call is dropped.


SIP INVITE received for an active dialog with Contact field identifying different IP address for CUCM to send messaging to.  This has to occur while a pending request is in place for the Dialog.
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