Allied Telesis AT-8100L/8POE, User Manual

Page: 98 / 330

Chapter 7: Spanning Tree Protocol on a Port
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
Version — Indicates the Spanning Tree Protocol version. The
default setting is RSTP.

Configured Path Cost — Enter the cost of the port to the root
bridge. This cost is combined with the costs of the other ports in
the path to the root bridge to determine the total path cost. The
lower the numeric value, the higher the priority of the path. The
range is 1 to 200,000,000. The default value is 0.

Priority (0-15) — Enter the priority value of the port. You can
influence which port is elected for a specific port role.
For example, when the switch has the two ports with the same
path cost, and the path cost is the lowest on the switch, it uses the
port priority value to determine which port is the root port.
If both priority values of these two ports are the same, the switch
elects a port with the lower port ID.
The range of the priority value is 0 to 240, in increments of 16, for a
total of 16 increments. See Table 1. Specify the increment of the
desired value. The default port priority is 128 (increment 8).

PortFast — Select “Enabled” to assign the port as an edge port, or
“Disabled” to assign the port as an non-edge port. Assign the port
as an edge port if the port is not connected to spanning tree
devices or to LANs that have spanning tree devices. An edge port
transitions from the blocking to forwarding state immediately so
that the host connected to the edge port can connect to the
network immediately, rather than waiting for spanning tree to
converge.
When an edge port starts to receive BPDUs, the switch no longer
considers the port as an edge port.
Table 1. STP Port Priority Value Increments
Increment
Port
Priority
Increment
Port
Priority
0 0 8 128
1 16 9 144
2 32 10 160
3 48 11 176
4 64 12 192
5 80 13 208
6 96 14 224
7 112 15 240