Operation Manual – MSTP
H3C S3100-52P Ethernet Switch
Chapter 1 MSTP Configuration
1-38
Rate
Operation mode
(half-/full-duplex)
802.1D-1998
IEEE 802.1t
Latency
standard
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.
II. 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.
