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Cisco Bug: CSCur18715 - CUCM native queue call disconnect due to Application AckTimer expire

Last Modified

Nov 27, 2020

Products (5)

  • Cisco 2600 Series Multiservice Platforms
  • Cisco 1000 Series Integrated Services Routers
  • Cisco 4000 Series Integrated Services Routers
  • Cisco ASR 1000 Series Aggregation Services Routers
  • Cisco Cloud Services Router 1000V Series

Known Affected Releases


Description (partial)

PSTN -- ISDN PRI -- Voice gateway -- SIP/H323 -- CUCM -- hunt pilot With Native Queue

When PSTN caller calls CUCM Native queue, the call will get disconnected after 60 seconds. Calls from PSTN disconnects with error "Application Ack Timer expired" seen in "debug isdn cc detail"

000774: Jul 31 14:06:07.036: ISDN Se0/0/0:15 **ERROR**: CCPCC_TApplnAckExpiry: Application Ack Timer expired. b channel 1 cref 0x808D call_id 0x004B

000775: Jul 31 14:06:07.036: %ISDN-4-STATUS: Interface Se0/0/0:15 Application AckTimer expired.  st 0x1407 ev 0x4B cid 0x808D cref 0x4B

The issue is seen only when TCL script is used on voice gateway as mentioned in the workaround of bug 
"CSCuh15872 CUCM9 Native Call Queuing should connect call on announcement"
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