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

Last Modified

Mar 10, 2020

Products (95)

  • Cisco IOS
  • Cisco 886VAG 3G Integrated Services Router
  • Cisco 888W Integrated Services Router
  • Cisco 892W Integrated Services Router
  • Cisco 886VA-CUBE Integrated Services Router
  • Cisco 812 CiFi Integrated Services Router
  • Cisco C892FSP Integrated Services Router
  • Cisco 2951 Integrated Services Router
  • Cisco VG204XM Analog Voice Gateway
  • Cisco 1905 Serial Integrated Services Router
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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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