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 device, the path cost may be different in different spanning tree instances. 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 device or through manual configuration.

Standards for calculating path costs of ports

Currently, the device can calculate the path costs of ports based on one of the following standards:

zdot1d-1998: Adopts the IEEE 802.1D-1998 standard to calculate the default path costs of ports.

zdot1t: Adopts the IEEE 802.1t standard to calculate the default path costs of ports.

zlegacy: Adopts the proprietary 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

 

 

 

 

 

 

 

Optional

 

 

 

 

 

calculating the default path

stp pathcost-standard

 

By default, the legacy standard

 

costs of the links connected to

{ dot1d-1998 dot1t legacy }

is used to calculate the default

 

the ports of the device

 

 

 

 

 

 

 

path costs of ports.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1-7Transmission speeds and the corresponding path costs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Transmissio

 

 

Operation mode

 

 

802.1D-1998

 

 

IEEE 802.1t

 

 

Proprietary

 

 

n speed

 

 

(half-/full-duplex)

 

 

 

 

 

 

standard

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

—

 

 

65,535

 

 

200,000,000

 

200,000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Half-duplex/Full-duplex

100

 

200,000

 

2,000

 

 

10 Mbps

 

Aggregated link 2 ports

95

 

 

1,000,000

 

1,800

 

 

 

Aggregated link 3 ports

95

 

 

666,666

 

1,600

 

 

 

 

 

 

 

 

 

 

 

 

 

Aggregated link 4 ports

95

 

 

500,000

 

1,400

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Half-duplex/Full-duplex

19

 

200,000

 

200

 

 

100 Mbps

 

Aggregated link 2 ports

15

 

 

100,000

 

180

 

 

 

Aggregated link 3 ports

15

 

 

66,666

 

160

 

 

 

 

 

 

 

 

 

 

 

 

 

Aggregated link 4 ports

15

 

 

50,000

 

140

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Full-duplex

 

 

4

 

 

200,000

 

20

 

 

1,000 Mbps

 

Aggregated link 2 ports

3

 

 

10,000

 

18

 

 

 

Aggregated link 3 ports

3

 

 

6,666

 

16

 

 

 

 

 

 

 

 

 

 

 

 

 

Aggregated link 4 ports

3

 

 

5,000

 

14

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Full-duplex

 

 

2

 

 

200,000

 

2

 

 

10 Gbps

 

Aggregated link 2 ports

1

 

 

1,000

 

1

 

 

 

Aggregated link 3 ports

1

 

 

666

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Aggregated link 4 ports

1

 

 

500

 

 

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.

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3Com WX3000 Configuring the Path Cost for a Port, Standards for calculating path costs of ports, Stp pathcost-standard