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Cisco Bug: CSCtd31242 - NEAT + IP Phone in Open Mode causes voice traffic to be dropped

Last Modified

Feb 27, 2018

Products (104)

  • Cisco Catalyst 2960 Series Switches
  • Cisco Catalyst 3750G-12S Switch
  • Cisco Catalyst 3560-12PC-S Compact Switch
  • Cisco Catalyst 3560E-48PD-SF Switch
  • Cisco ME 3400-24TS-A Switch
  • Cisco Catalyst 3560E-12D-E Switch
  • Cisco Catalyst 3560E-24TD-S Switch
  • Cisco Catalyst 3750V2-24PS Switch
  • Cisco Catalyst 3560E-48PD-E Switch
  • Cisco Catalyst 2960-48TT-S Switch
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Known Affected Releases


Description (partial)


In a NEAT setup where the SSw authenticates with the ASw and an IP phone authenticates with the SSw via MAB (after dot1x times out) in Open Mode. IP phone gets network access and a call is placed successfully from IP phone. Suddenly, without any change in the state of the network, IP phone looses its connectivity to the network after about 5mins.

This is as a result of the phone's MAC address being removed from the Voice VLAN on the ASw's CAM table, causing traffic to be dropped upstream on the ASw.

The issue is only seen when the ASw = 3750 and SSw = 2960 running 12.2(52)SE code and an IP phone authenticates in Open Mode on the SSw.
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