Allied Telesis FORMULA 8200 - Manual (Page 39)

FORMULA 8200 User’s Guide
3-7
In addition to preventing looping, Spanning Tree provides the
following functions:
❑ Automatic reconfiguring of the topology in the event of a
failure or the addition of a bridge or a bridged port
❑ Topology stability, regardless of the size of the bridged VLAN
❑ Configuration management, by displaying statistics and user-
specified bridge and port priorities, parameters, and timers
Spanning Tree performs the above functions by exchanging BPDUs
(Bridge Protocol Data Units) packets between bridges. When the
topology changes, the time it takes for Spanning Tree to stabilize
depends on the size of the bridged network and several user-
configurable parameters.
Spanning Tree Protocol functions by putting its ports in the following
modes or states:
Blocking State - In this state, ports do not forward packets
and do not learn addresses. The ports are in standby mode
until a topology change occurs.
Listening State - In this state, ports do not forward packets
and do not learn addresses.
Learning State - In this state, ports do not forward packets in
either direction, but they learn station addresses.
Forwarding State - In this state, ports forward and learn all
packets in either direction.
The listening state and learning state are both temporary states as
the port moves into forwarding state.
Use the VBRIDGE/SHOW/BRIDGE command to view the
current configuration settings.
To enable and configure Spanning Tree, use the VBRIDGE/CONFIG/
BRIDGE command, or refer to Configuring a Virtual
Bridge later in this chapter
.