H3C S3100-52P Operation Manual page 282

Operation Manual – MSTP
H3C S3100-52P Ethernet Switch
Rate
100 Mbps
1,000
Mbps
10 Gbps
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:
Where, "link transmission rate" is the sum of the rates of all the unblocked ports on the
aggregated link measured in 100 Kbps.
II. Configure the path cost for specific ports
Follow these steps to configure the path cost for specified ports in system view:
Enter system view
Configure the path cost
for specified ports
Operation mode
(half-/full-duplex)
Half-duplex/Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports
Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports
Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports
Path cost = 200,000,000 / link transmission rate
To do...
System-view
stp interface interface-list
[ instance instance-id ]
cost cost
802.1D-1998
19
15
15
15
4
3
3
3
2
1
1
1
Use the command...
1-38
Chapter 1 MSTP Configuration
Latency
IEEE 802.1t
standard
200,000 200
100,000 180
66,666 160
50,000 140
20,000 20
10,000 18
6,666 16
5,000 14
2,000 2
1,000 1
666 1
500 1
Remarks
—
Required
An MSTP-enabled switch
can calculate path costs
for all its ports
automatically.