Spanning Tree Protocol - Cisco N5K-M1600 - Expansion Module - 6 Ports Troubleshooting Manual

Chapter 3 Troubleshooting Layer 2 Switching Issues
S e n d d o c u m e n t c o m m e n t s t o n e x u s 5 k - d o c f e e d b a c k @ c i s c o . c o m .
Traffic flooding in a VPC setup
Data is not getting forwarded, instead it is being flooded in the presence of a VPC scenario.
Possible Cause
The MAC address is learned on one switch only. Typically, this situation would be a bug regarding the
synchronization of the MAC address with the VPC peer.
Solution
Clear the MAC address from the switch where it was learned. This triggers new learning and
synchronization of the MAC addresses across the VPC switches.

Spanning Tree Protocol

HIFs go down with the BPDUGuard errDisable message
HIFs go down accompanied with the message, BPDUGuard errDisable.
Possible Cause
By default, the HIFs are in STP edge mode with the BPDU guard enabled. This means that the HIFs are
supposed to be connected to hosts or non-switching devices. If they are connected to a non-host
device/switch that is sending BPDUs, the HIFs become error-disabled upon receiving a BPDU.
Solution
Enable the BPDU filter on the HIF and on the peer connecting device. With the filter enabled, the HIFs
do not send or receive any BPDUs. Use the following commands to confirm the details of the STP port
state for the port:
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FWM-2-STM_LOOP_DETECT detected on switch, dynamic learning disabled
When FWM-2-STM_LOOP_DETECT is detected on the switch, dynamic learning is disabled.
Possible Cause
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•
Use the following commands to verify the STP port state across VLANS on the switches:
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Solution
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OL-25300-01
show spanning-tree interface <id> detail
show spanning-tree interface <id>
MAC addresses are moving because of incorrect STP-port state convergence.
MAC addresses are moving because the source of the data being physically moved across all
switches while STP states are converged and in correct states.
show spanning-tree
show spanning-tree vlan <id>
Check for a correct STP convergence and for STP port states across all switches in the topography.
Also confirm that there are no disputes or incorrect port states.
Cisco Nexus 5000 Series Troubleshooting Guide
Spanning Tree Protocol
3-3