HP proliant bl e-class Manual De Usuario

This section describes several troubleshooting tips. 

A failure in the STP 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 to transition its Port 
2 from the blocking state to the forwarding state. 

 

NOTE:  A port must continue to receive BPDUs advertising superior paths to remain in the blocking 
state. 

There are a number of circumstances in which STP can fail, mostly related to the loss of a 
large number of BPDUs. These situations will cause a port in the blocking state to transition 
to the forwarding state.