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Cisco Bug: CSCsg31865 - MGCP CAS trunk intermittently sends back 501 response when glare occurs

Last Modified

Feb 22, 2014

Products (1)

  • Cisco 2800 Series Integrated Services Routers

Known Affected Releases


Description (partial)


Inbound and outbound on a Cisco IOS VoIP gateway calls stop processing through a trunk on a MGCP controlled CAS circuit.  When the Cisco CallManager is used as the Call Agent, inbound calls from the PSTN may experience dead-air.


Intermittently under some glare conditions (when the MGCP controlled timeslots are accessed simultaneously for an inbound and outbound call), the IOS gateway may respond to a Call Agent MGCP command with a 501 response. When the Call Agent is a Cisco Callmanager, this response code will cause the Callmanager to place the trunk into a out-of-service (OOS) state until manual intervention just as resetting the GW or shut/no-shut takes place on the gateway.
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