Allied Telesis AT-GS950/16PS, Руководство пользователя

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AT-GS950/16PS Switch Web Interface User’s Guide
65
.
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 may take time for the root bridge to notify all bridges that a topology
change has occurred, especially if it is a large network. A temporary data
loop could occur if a topology change is made before all bridges have
been notified and that could adversely impact network performance.
To forestall the formation of temporary 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 states the amount of time that a port
spends in the listening and learning states prior to changing to the
forwarding state.
Table 2. Valid Port Priority Values
Step
Port
Priority
1 0
2 16
3 32
4 48
5 64
6 80
7 96
8 112
9 128
10 144
11 160
12 176
13 192
14 208
15 224
16 240