Allied Telesis AT-S25 - Manual (Page 48)

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Hello Time
Bridges use this parameter to determine the time interval
between generating and sending configuration messages. This
parameter can be from 1 to 10 seconds. The default is 2 seconds.
Forwarding Delay
This parameter indicates the waiting period before a bridge
changes to a new state, for example, becomes the new root
bridge after the topology changes. If the bridge transitions too
soon, not all links may have yet adapted to the change; therefore,
loops may result. The default is 15 seconds.
Caution
You should consult the IEEE 802.1d standard before changing the
Max Age Time, the Hello Time, and the Forwarding Delay
parameters.
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