3com 3C16491 Manuel D’Utilisation

This administrative tool supports the 
configuration of the Switch to forward, or 
block and discard 802.1D spanning tree BPDU 
packets.

Spanning tree is a bridge-based system for 
providing fault tolerance on networks and can 
be used to detect and disable network loops. 
The spanning tree ensures that the optimal 
path is maintained between spanning 
tree-compliant networked devices by:

■

Disabling redundant paths when the main 
paths are operational.

■

Enabling redundant paths if the main paths 
fail.

Spanning tree uses a distributed algorithm to 
select a bridging device that serves as the root 
of the spanning tree network. The bridging 
device known as the Root Bridge generates 
BPDUs (Bridge Protocol Data Units) on all ports 
at a regular interval known as the Hello Time. 
All other spanning tree-compliant devices on 
the network have a designated Root Port. This 
is the Port nearest the Root Bridge and it is 

used for receiving the BPDUs initiated by the 
Root Bridge. If a bridge does not get a Hello 
BPDU after a predetermined interval, the bridge 
assumes that the link to the Root Bridge is 
down. This bridge will then initiate negotiations 
with other bridges to reconfigure the network 
to re-establish a valid network topology.

After all the bridges on the network have 
determined the configuration of their ports, 
each bridge only forwards traffic between the 
Root Port and the ports that are the Designated 
Bridge Ports for each network segment. All 
other ports are blocked, which means that they 
are prevented from forwarding traffic.

Three tabs are available on the Spanning Tree 
per Port page:

■

Summary

■

Detail

■

Setup