Cisco N5K-M1600 - Expansion Module - 6 Ports Troubleshooting Manual page 46

Spanning Tree Protocol
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 .
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Port stuck in STP blocking state with BLK*(Type_Inc)
A port is stuck in STP blocking state with BLK*(Type_Inc).
Possible Cause
A type inconsistency might exist on an access port when it is connected to a trunk port on the other end.
The port becomes BLK*(Type_Inc) to indicate that there is an incorrect configuration on the link. Use
the following commands to confirm the details of the STP port state for the port:
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Solution
Check the switch port modes configured at both ends (ports) of the link. Ensure that they are in the same
mode. Both should be in access or trunk mode. Once the modes are synchronized, the port moves out of
the inconsistency state.
Port stuck in STP blocking state with BLK*(PVID_Inc)
A port is stuck in STP blocking state with BLK*(PVID_Inc).
Possible Cause
A PVID inconsistency may exist when there is a native VLAN mismatch across a trunk link. When this
occurs, the port state becomes BLK* (PVID_Inc). Use the following commands to confirm the details
of the STP port state for the port:
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Solution
Check the native VLAN configured at both ends (ports) of the link. Ensure that they have the same native
VLAN. Once the native VLANs are synchronized, the port moves out of the inconsistency state.
Port stuck in STP blocking state with BLK*(Loop_Inc)
A port is stuck in STP blocking state with BLK*(Loop_Inc).
Possible Cause
This situation occurs when the loop guard is configured on the port and the port stops receiving BPDUs.
This is supposed to prevent loops when unidirectional link failures occur. However, the port is put into
a BLK* (Loop_Inc) state. Use the following commands to confirm the details of the STP port state for
the port:
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Cisco Nexus 5000 Series Troubleshooting Guide
3-4
If the source of the data frames, which are physically moving, is identified, then control the source
to halt rapid and continuous moves.
By default, dynamic learning is opened after 180 seconds. At that point, any STP disputes or
inconsistencies should be resolved.
show spanning-tree interface <id> detail
show spanning-tree interface <id>
show spanning-tree interface <id> detail
show spanning-tree interface <id>
show spanning-tree interface <id> detail
show spanning-tree interface <id>
Chapter 3 Troubleshooting Layer 2 Switching Issues
OL-25300-01