Allied Telesis AT-8100 Series - Manual (Page 796)

Chapter 54: Spanning Tree Protocol (STP) Procedures
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Designating STP as the Active Spanning Tree Protocol
Before you can configure the STP parameters or enable the protocol on
the switch, you have to designate STP as the active spanning tree
protocol. The switch supports other spanning tree protocols in addition to
STP, but only one of them can be active at a time on the device.
To designate STP as the active spanning tree protocol on the switch, use
the SPANNING-TREE MODE STP command in the Global Configuration
mode. Here is the command:
awplus> enable
awplus# configure terminal
awplus(config)# spanning-tree mode stp
After you enter the command, you can configure the STP parameters and
enable the protocol so that the switch begins to use the protocol.