Configuring path costs of ports – H3C Technologies H3C WX3000E Series Wireless Switches User Manual
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Configuring path costs of ports
Path cost is a parameter related to the rate of a port. On a spanning tree device, a port can have different
path costs in different MSTIs. Setting appropriate path costs allows VLAN traffic flows to be forwarded
along different physical links, achieving VLAN-based load balancing.
The device can automatically calculate the default path cost; alternatively, you can also configure the
path cost for ports.
Specifying a standard for the device to use when calculating the default path cost
You can specify a standard for the device to use in automatic calculation for the default path cost. The
device supports the following standards:
•
dot1d-1998: The device calculates the default path cost for ports based on IEEE 802.1d-1998.
•
dot1t: The device calculates the default path cost for ports based on IEEE 802.1t.
•
legacy: The device calculates the default path cost for ports based on a private standard.
Follow these steps to specify a standard for the device to use when calculating the default path cost:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Specify a standard for the device
to use when calculating the default
path costs of its ports
stp pathcost-standard
{ dot1d-1998 | dot1t | legacy }
Optional
legacy by default.
CAUTION:
If you change the standard that the device uses in calculating the default path costs, you restore the path
costs to the default.
NOTE:
When calculating path cost for an aggregate interface, IEEE 802.1t takes into account the number of
Selected ports in its aggregation group, but IEEE 802.1d-1998 does not. The calculation formula of IEEE
802.1t is: Path Cost = 200,000,000/link speed (in 100 kbps), where link speed is the sum of the link
speed values of the Selected ports in the aggregation group.
shows the mappings between the link speed and the path cost.
Table 13 Mappings between the link speed and the path cost
Link speed
Port type
Path cost
IEEE
802.1d-1998
IEEE 802.1t
Private standard
0 —
65535
200,000,000
200,000
10 Mbps
Single Port
100
2,000,000 2,000
Aggregate interface
containing 2 Selected ports
1,000,000 1,800
Aggregate interface
containing 3 Selected ports
666,666 1,600
Aggregate interface
containing 4 Selected ports
500,000 1,400