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198 CHAPTER 8: STP OPERATION
Configuring the Path
Cost of a Port
Path cost is related to the speed of the link connected to the port. On the MSTP
switch, a port can be configured with different path costs for different STIs. Thus
the traffic from different VLANs can run over different physical links, thereby
implementing the VLAN-based load-balancing.
You can configure the path cost of a port in the following ways.
Configuring in System View
Perform the following configuration in system view.
Configuring in Ethernet Port View
Perform the following configuration in Ethernet port view.
For more about the commands, see the Switch 7750 Command Reference Guide.
Upon the change of path cost of a port, MSTP will recalculate the port role and
transit the state. When instance-id takes 0, it indicates to set the path cost on the
CIST.
By default, MSTP is responsible for calculating the port path cost.
Specify the Standard To BeFollowed in Path Cost Calculation
The following two standards are currently available on the switch:
■ dot1d-1998: The switch calculates the default Path Cost of a port by the IEEE
802.1D-1998 standard.
■ dot1t: The switch calculates the default Path Cost of a port by the IEEE 802.1t
standard.
■ legacy: The switch calculates the default Path Cost of a port by the
Huawei-3Com standard.
You can specify the intended standard by using the following commands.
Table 202 Configure the Path Cost of a Port
Operation Command
Configure the Path Cost of a port. stp interface interface-list
instance instance-id cost cost
Restore the default path cost of a port. undo stp interface interface-list
instance instance-id cost
Table 203 Configure the Path Cost of a Port
Operation Command
Configure the Path Cost of a port stp instance instance-id cost
cost
Restore the default path cost of a port. undo stp instance instance-id
cost