Allied Telesis AT-S63 User Manual
Page 425
AT-S63 Management Software Menus Interface User’s Guide
Section V: Spanning Tree Protocols
425
1 - Port Priority
This parameter is used as a tie breaker when two or more ports have
equal costs to the root bridge. The range is 0 to 240 in increments of
16. The default value is 8 (priority value 128). Table 6 lists the
increments.
2 - Port Cost
The spanning tree algorithm uses the cost parameter to decide which
port provides the lowest cost path to the root bridge for that LAN. The
range is 0 to 65,535. The default setting is Automatic Update, which
sets port cost depending on the speed of the port. Table 9 lists the STP
port costs with Auto-Detect.
Table 8 lists the STP port costs with Auto-Detect when a port is part of
a port trunk.
Table 6. Port Priority Value Increments
Increment
Bridge
Priority
Increment
Bridge
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
Table 7. STP Auto-Detect Port Costs
Port Speed
Port Cost
10 Mbps
100
100 Mbps
10
1000 Mbps
4
Table 8. STP Auto-Detect Port Trunk Costs
Port Speed
Port Cost
10 Mbps
4
100 Mbps
4