D-Link DES-3326S manual Troubleshooting STP, Spanning Tree Protocol Failure

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

Troubleshooting STP

Spanning Tree Protocol Failure

A failure in the STA generally leads to a bridging loop. A bridging loop in an STP environment comes from a port that should be in the blocking state, but is forwarding packets.

In this example, B has been elected as the designated bridge and port 2 on C is in the blocking state. The election of B as the designated bridge is determined by the exchange of BPDUs between B and C. B had a better BPDU than C. B continues sending BPDUs advertising its superiority over the other bridges on this LAN. Should C fail to receive these BPDUs for longer than the MAX AGE (default of 20 seconds), it could start

330Understanding and Troubleshooting the Spanning Tree Protocol