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Cisco Bug: CSCum26615 - Secure SIP 7942/7962 Phones Unregister when BLF with Call List Enabled

Last Modified

Mar 03, 2018

Products (36)

  • Cisco Unified IP Phone 7900 Series
  • Cisco Unified Wireless IP Phone 7920
  • Cisco Unified IP Phone 7945G
  • Cisco Unified IP Phone 7971G-GE
  • Cisco Unified IP Phone 7962G
  • Cisco Unified IP Phone Expansion Module 7914
  • Cisco Unified IP Phone 9951
  • Cisco Unified IP Phone 7941G
  • Cisco Unified IP Phone 6961
  • Cisco Unified IP Phone 6941
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Known Affected Releases


Description (partial)

Secure SIP 7942 Phones (Authenticated or Encrypted) will unregister with CUCM when BLF with Call List is enabled.  This behavior is seen in environments where marginal packet loss (1% drop) is observed, and the packet drop originates in the direction of Phone to CUCM across network topology in use.

Behavior observed during this fault is a TCP FIN/ACK sent by the Phone to CUCM after entering into TCP Retransmission phase and exceeding it's TCP window size, at which point the Phone will re-register to CUCM.

1) Phone Configuration - Device Security Profile set to SIP Secure (Authenticated or Encrypted)
2) Enterprise Parameter - BLF For Call List set to Enabled
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Bug Details Include

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