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Configuring the Path Cost for a Port
The path cost parameter reflects the rate of the link connected to the port. For a port on an
MSTP-enabled switch, the path cost may be different in different MSTIs. You can enable flows of
different VLANs to travel along different physical links by configuring appropriate path costs on ports, so
that VLAN-based load balancing can be implemented.
Path cost of a port can be determined by the switch or through manual configuration.
Standards for calculating path costs of ports
Currently, a switch can calculate the path costs of ports based on one of the following standards:
z dot1d-1998: Adopts the IEEE 802.1D-1998 standard to calculate the default path costs of ports.
z dot1t: Adopts the IEEE 802.1t standard to calculate the default path costs of ports.
Follow these steps to specify the standard for calculating path costs:
To do... Use the command... Remarks
Enter system view
system-view
—
Specify the standard for
calculating the default path
costs of the links connected to
the ports of the switch
stp pathcost-standard
{ dot1d-1998 | dot1t }
Optional
By default, the dot1t standard is
used to calculate the default
path costs of ports.
Table 1-7 Transmission rates vs. path costs
Rate Operation mode (half-/full-duplex) 802.1D-1998 IEEE 802.1t
0 — 65,535 200,000,000
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
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
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
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
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.