Allied Telesis AT-GS950/24 - Manual (Page 136)

Chapter 9: Multiple Spanning Tree Protocol
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bridge spends in the listening and learning states. Its range is
4 - 30 seconds.
Maximum Hop Count - The Maximum Hop Count is a parameter
set in a BPDU packet when it originates. It is decremented by 1
each time it is retransmitted by the next bridge. When the Hop
Count value reaches zero, the bridge drops the BPDU packet. Its
range is 6 - 40 hops.
Transmit Hold Count - The Transmit Hold Count specifies the
maximum number of BPDUs that the bridge can send per second.
Its range is 1 - 10.
5. Once you have configured the parameters, click Apply.
6. From the main menu on the left side of the page, select Save
Configuration to Flash to permanently save your changes.