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Cisco Bug: CSCuq61271 - 69xx phones re-using source port after power is removed

Last Modified

Jul 20, 2015

Products (35)

  • Cisco IP Phone 8800 Series
  • Cisco Unified IP Phone Expansion Module 7914
  • Cisco Unified IP Phone 7945G
  • Cisco Unified IP Phone 9951
  • Cisco Unified Wireless IP Phone 7920
  • Cisco Unified IP Phone 7962G
  • Cisco Unified IP Phone 7971G-GE
  • Cisco Unified IP Phone 7911G
  • Cisco Unified IP Phone 6961
  • Cisco Unified IP Phone 6941
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Known Affected Releases


Description (partial)

69xx phones re-using source port after power is removed

TCP source port for SIP used by phone after an electrical failure is not randomly chosen.

Source port used is the same as the one which was previoulsy used just before the electrical failure.

As the tcp connection was not properly terminated, the firewall assume that it is still up, and reject all the 
TCP SYN from the same source port.

It takes more than 10 minutes for the phone to register

SIP    after power is removed in 69xx phones
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