Hello, If you enable bpduguard globally and an interface was to receive a bpdu, it would go in to err-disable. It is one of the causes for errdisable - if you wasn't expecting this, please investigate what device is connected to the ports and why you would have received this bpdu. But please remember that there are other reasons for a port to go to error disable mode too, so it doesnt necesssarily have to be because of the bpdu guard.
If you do a 'show errdisable recovery' command, it will show you the reason why the port got shut in to that state.
Causes of Errdisable
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. Late collisions occur after every device on the wire should have recognized that the wire was in use. Possible causes of these types of errors include:
- A cable that is out of specification (either too long, the wrong type, or defective)
- A bad network interface card (NIC) card (with physical problems or driver problems)
- A port duplex misconfigurationA 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.
There are various reasons for the interface to go into errdisable. The reason can be:
- Duplex mismatch
- 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
Please see here for more details:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00806cd87b.shtml
Hope this helps
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Please rate useful posts & remember to mark any solved questions as answered. Thank you.
