R3303-HP HSR6800 Routers Layer 2 - LAN Switching Configuration Guide

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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.
You can have the device automatically calculate the default path cost, or you can configure the path cost
for ports.
Specifying a standard for the device to use when it calculates
the default path cost
CAUTION:
If you change the standard that the device uses to calculate the default path costs, you restore the path
costs to the default.
You can specify a standard for the device to use in automatic calculation of the default path cost. The
device supports the following standards:
• dot1d-1998—The device calculates default path costs for ports based on IEEE 802.1d-1998.
• dot1t—The device calculates default path costs for ports based on IEEE 802.1t.
• legacy—The device calculates default path costs for ports based on a private standard.
Table 12 sh
ows a comparison between link speeds and path costs for each of these standards.
Table 12 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 N/A 65535 200000000 200000
10 Mbps
Single port
100
2000000 2000
Aggregate interface
containing 2 Selected ports
1000000 1800
Aggregate interface
containing 3 Selected ports
666666 1600
Aggregate interface
containing 4 Selected ports
500000 1400
100 Mbps
Single port
19
200000 200
Aggregate interface
containing 2 Selected ports
100000 180
Aggregate interface
containing 3 Selected ports
66666 160
Aggregate interface
containing 4 Selected ports
50000 140
1000 Mbps Single port 4 20000 20