Allied Telesis AT-S20 - Manual (Page 60)

Configuring for Bridging
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3. Enter Max age time to get the next screen and enter the aging
time in seconds at the prompt.
The aging time can be from 6-40 seconds, with 20 seconds as a
default. All bridges in a bridged LAN use this aging time to test the
age of stored configuration messages called bridge protocol data
units (BPDUs).
For example, if you use the default 20, all bridges delete current
configuration messages after 20 seconds.
Note
Aging time for BPDUs are different from aging time in the MAC
address table.
4. Enter Hello time and enter the time in seconds at the prompt.
Hello time can be from 1-10 seconds, with 2 seconds as the
default. Bridges use this parameter to determine the time interval
between generating and sending configuration messages.
5. Enter Forwarding delay value and enter the time in seconds.
The default is 15 seconds. The time 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.
6. Select Return to Main Menu and repeat the procedure if you
want to reconfigure the spanning tree parameters for
Administration.