Allied Telesis AT-S29 - Manual (Page 120)

Advanced Topics
120
Once a stable network topology has been established, all bridges listen
for Hello BPDUs (Bridge Protocol Data Units) transmitted from the Root
Bridge. If a bridge does not get a Hello BPDU after a predefined interval
(Maximum Age), 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.
The following figure gives an illustration of how the Spanning Tree
Algorithm assigns bridging device ports.
Using STA and
Trunk Ports
The Spanning Tree Algorithm will treat a trunk as a whole instead of
individual ports. STA will determine the path cost and path priority of a
trunk connection based on the first port. However, the states of
individual trunk ports are determined based on individual link status.
Remember that the first port of a trunk MUST be connected to make sure
STA works properly.
Root Bridging
Device
Designated Port Designated Port
Designated Port
Designated Port
Root Port Root Port Root Port
Root Port
Designated Port
Root Port
Blocking