Path cost
Link speed
Port type
IEEE
802.1d-1998
IEEE 802.1t
Private standard
Aggregate interface
containing 3 selected ports
666 1
Aggregate interface
containing 4 selected ports
500 1
NOTE:
When calculating path cost for an aggregate interface, IEEE 802.1d-1998 does not take into account the
number of selected ports in its aggregation group as IEEE 802.1t does. 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.
Configuring path costs of ports
Follow these steps to configure the path cost of ports:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Enter Ethernet interface
view or Layer 2 aggregate
interface view
interface
interface-type
interface-number
Enter interface
view or port
group view
Enter port group view
port-group manual
port-group-name
Required
Use either command.
Configure the path cost of the ports
stp
[
instance
instance-id
]
cost
cost
Required
By default, MSTP
automatically calculates the
path cost of each port.
CAUTION:
When the path cost of a port changes, MSTP re-calculates the role of the port and initiates a state
transition.
Configuration example
# Specify that the device uses IEEE 802.1d-1998 to calculate the default path costs of its ports.
<Sysname> system-view
[Sysname] stp pathcost-standard dot1d-1998
# Set the path cost of Ethernet 1/0/3 on MSTI 2 to 200.
<Sysname> system-view
[Sysname] interface ethernet 1/0/3
[Sysname-Ethernet1/0/3] stp instance 2 cost 200
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