Allied Telesis AT-S25 - Manual (Page 96)

Section II: Local and Telnet Mangement
96
Port Priority
If two paths have the same port cost, the bridges must select a preferred
path. In some instances this can involve the use of the port priority
parameter. This parameter can be used as a tie-breaker when two paths
have the same cost.
The port priority has a range of from 0 to 240. As with the bridge priority,
this range is broken into increments, in this case multiples of 16. When
you specify a port priority for a port, you enter the increment of the
desired value.
Forwarding Delay and Topology Changes
If there is a change in the network topology due to a failure, removal, or
addition of any active components, the active topology also changes.
This may trigger a change in the state of some blocked ports. However, a
change in a port state is not activated immediately.
It might take time for the root bridge to notify all bridges that a topology
change has occurred, especially if it is a large network. If a topology
change is made before all bridges have been notified, a temporary data
loop could occur, and that could adversely impact network
performance.
Table 8 Port Priority Value Increments
Increment
Bridge
Priority
Increment
Bridge
Priority
0 0 8 128
1 16 9 144
2 32 10 160
3 48 11 176
4 64 12 192
5 80 13 208
6 96 14 224
7 112 15 240