3Com Switch 8800 Configuration Guide Chapter 38 MSTP Region-configuration
38-25
The actual rate counts.
2) Calculating the path cost
z Full-duplex and non-aggregation port at a rate less than 1 GE
Path cost = [200,000,000 / (rate × 10)] – 1
z Other ports
Path cost = 200,000,000 / (rate × 10)
II. DOT1D-1998 calculation standard 1) Calculating the rate
z Aggregation port
If the port is up, the actual rate counts. If the port is down, the rate is determined by that
of the port which goes up first in the aggregation group. If all the ports in the
aggregation group are down, the rate of the aggregation port is 0.
z Non-aggregation port
The actual rate counts.
2) Calculating the path cost
Table 38-17 details the correspondence between the rate range and the path cost
values of the ports.
Table 38-17 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] 2 (for aggregation port)
1 (default)
> 10000 1
1) Calculating the rate
z Aggregation port