3Com Switch 8800 Family Configuration Guide

Configuring MSTP 143
The actual rate counts.
2 Calculating the path cost
Table 121 details the correspondence between the rate range and the path cost
values of the ports.
3Com’s legacy calculation standard
1 Calculating the rate
■ Aggregation port
The rate of the primary port in an aggregation group is determined by the sum of
the port rates in this group. No calculation is performed for secondary port.
■ Non-aggregation port
The actual rate counts, but the rate is 0 if the port is down.
2 Calculating the path cost
Table 122 details the correspondence between the rate range and the value range
of the path cost of the ports.
You can specify the intended standard by using the following commands.
Perform the following configuration in system view.
Tab le 121 Correspondence between the rate range and the PATH cost values
Rate range PATH cost value
[0, 10]
99 (for full-duplex port)
95 (for aggregation port)
100 (default)
(10, 100]
18 (for full-duplex port)
15 (for aggregation port)
19 (default)
(100,1000]
3 (for aggregation port)
4 (default)
(1000,10000]
1 (for aggregation port)
2 (default)
> 10000 1
Tab le 122 Correspondence between the rate range and PATH cost range
Rate range PATH cost range
[0, 100] 2200 to (20 × rate)
(100,1000] 220 to the integer of [(0.2 × rate)]
(1000,10000] 22 to the integer of [(0.002 × rate)]
> 10000 1