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Cisco Bug: CSCus38175 - Native VLAN Removed from Spanning-tree with 'no macro auto monitor'

Last Modified

Jan 19, 2017

Products (1)

  • Cisco Catalyst 4000 Series Switches

Known Affected Releases

15.2(1)E

Description (partial)

Symptom:
When applying the 'no macro auto monitor' command you will notice that all trunk interfaces go down if there are two trunked interfaces, not in a port-channel, connected from the 4500x VSS to a remote switch. The trunked interfaces go down as a result of the native VLAN being removed from Spanning-Tree.

The following output will be see when the interface goes down, after applying 'no macro auto monitor'
*Dec 22 08:07:24.635: %DTP-5-NONTRUNKPORTON: STANDBY:Port Te1/1/5,Te2/1/5 has become non-trunk

Output of show spanning-tree <native vlan> will show that vlan does no exist in spanning tree:
4500x-VSS#sho spanning-tree vlan 1

Spanning tree instance(s) for vlan 1 does not exist.

Conditions:
Applying the 'no macro auto monitor' command on a 4500 VSS running 3.5.X version of IOS with two trunk interfaces, not configured as a port-channel, connected to a remote switch.
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