Allied Telesis AT-S63 - Manual (Page 423)

AT-S63 Management Software Menus User’s Guide
Section V: Spanning Tree Protocols 423
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