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Cisco Bug: CSCtb67958 - MST to Rapid-PVST+ fails to operate with loop guard enabled

Last Modified

Feb 13, 2018

Products (96)

  • Cisco Catalyst 3560 Series Switches
  • Cisco Catalyst 3750V2-24PS Switch
  • Cisco Catalyst 2960-24-S Switch
  • Cisco Catalyst 3560E-24TD-S Switch
  • Cisco Catalyst 3560E-48PD-SF Switch
  • Cisco Catalyst 3560-12PC-S Compact Switch
  • Cisco Catalyst 3750G-12S Switch
  • Cisco ME 3400-24TS-A Switch
  • Cisco ME 3400EG-2CS-A Switch
  • Cisco Catalyst 2960-48TT-S Switch
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Known Affected Releases

12.2(44)SE5 12.2(50)SE3

Description (partial)

When the spanning tree protocol is changed on a root bridge from Rapid-PVST+ to MST and if loop guard is present on the ports attached to other Rapid-PVST+ bridges, the vlan goes into inconsistent state.

Spanning tree loop guard is present on ports interconnecting Rapid-PVST+ bridges and subsequently the spanning tree protocol is changed to MST on the root bridge.
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