Allied Telesis AT-S60 - Manual (Page 233)

AT-S60 Management Software User’s Guide
Section II: Advanced Features 233
The range for port priority is 0 to 240 in increments of 16. Just as with the
bridge priority value, you specify the increment that corresponds to the
desired value. Table 11 lists the port priority increments. The default
value is 128, with an increment of 8.
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 may also
change. 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.
To forestall the formation of temporarily data loops during topology
changes, a port designated to change from blocking to forwarding
passes through two additional states, listening and learning, before it
begins to forward frames. The amount of time a port spends in these
states is set by the forwarding delay value. This value controls the
amount of time that a port spends in the listening and learning states
prior to changing to the forwarding state.
Table 11 Port Priority Value Increments
Increment
Port
Priority
Increment
Port
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