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Cisco Switch: Unexpected BPDU received. Port has been Disabled

Situation: Cisco switch logs this message: Description: Gi3/0/15: Unexpected BPDU received. Port has been Disabled. Based on Cisco, “This feature was first implemented to handle special collision situations in which the switch detected excessive or late collisions on a port. Excessive collisions occur when a frame is dropped because the switch encounters 16 collisions in a row”.

Case 1: The cable is defective. Replacing the cable works fine.

Case 2: The NIC has an issue. Upgrading the the driver fixes the problem.

Case 3: It is port duplex mis-configuration.Based on Cisco: “A port duplex misconfiguration is a common cause of the errors because of failures to negotiate the speed and duplex properly between two directly connected devices (for example, a NIC that connects to a switch). Only half-duplex connections should ever have collisions in a LAN. Because of the carrier sense multiple access (CSMA) nature of Ethernet, collisions are normal for half duplex, as long as the collisions do not exceed a small percentage of traffic”.

The following lists could be the issue too.

·      Port channel misconfiguration

·      BPDU guard violation

·      UniDirectional Link Detection (UDLD) condition

·      Late-collision detection

·      Link-flap detection

·      Security violation

·      Port Aggregation Protocol (PAgP) flap

·      Layer 2 Tunneling Protocol (L2TP) guard

·      DHCP snooping rate-limit

·      Incorrect GBIC / Small Form-Factor Pluggable (SFP) module or cable

·      Address Resolution Protocol (ARP) inspection

·      Inline power

Note: Error-disable detection is enabled for all of these reasons by default. In order to disable error-disable detection, use the no errdisable detect cause command. The show errdisable detect command displays the error-disable detection status.

More case can be found here: Unexpected BPDU received. Port has been Disabled

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