H3C Technologies H3C S3100 Series Switches - Manual (Page 250)

1-31
Table 1-7 Transmission rates vs. path costs
Rate
Operation mode
(half-/full-duplex)
802.1D-1998 IEEE 802.1t
Latency
standard
0 — 65,535 200,000,000 200,000
10 Mbps
Half-duplex/Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports 100
95
95
95 2,000,000
1,000,000
666,666
500,000 2,000
1,800
1,600
1,400
100 Mbps
Half-duplex/Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports 19
15
15
15 200,000
100,000
66,666
50,000 200
180
160
140
1,000 Mbps
Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports 4
3
3
3 20,000
10,000
6,666
5,000 20
18
16
14
10 Gbps
Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports 2
1
1
1 2,000
1,000
666
500 2
1
1
1
Normally, the path cost of a port operating in full-duplex mode is slightly less than that of the port
operating in half-duplex mode.
When calculating the path cost of an aggregated link, the 802.1D-1998 standard does not take the
number of the ports on the aggregated link into account, whereas the 802.1T standard does. The
following formula is used to calculate the path cost of an aggregated link:
Path cost = 200,000,000 / link transmission rate
Where, “link transmission rate” is the sum of the rates of all the unblocked ports on the aggregated link
measured in 100 Kbps.
Configure the path cost for specific ports
Follow these steps to configure the path cost for specified ports in system view:
To do... Use the command... Remarks
Enter system view system-view —
Configure the path cost for
specified ports
stp interface interface-list
[ instance instance-id ] cost
cost
Required
An MSTP-enabled switch can
calculate path costs for all its
ports automatically.