Allied Telesis AT-S39 - Manual (Page 249)

Section III: Web Browser Management
249
Configuring STP
Caution
The bridge provides default STP parameters that are adequate for
most networks. Changing them without prior experience and an
understanding of how STP works might have a negative effect on
your network. You should consult the IEEE 802.1d standard before
changing any of the STP parameters.
1. From the Spanning Tree tab window, click STP Configuration and
click Configure.
The Spanning Tree window in Figure 82 is displayed.
Figure 82 STP Bridge Configuration Window