87
Link speed
Port type
Path cost
IEEE 802.1d-1998
IEEE 802.1t
Private standard
10 Gbps
Single port
2
2000 2
Aggregate interface
containing 2 Selected ports
1000 1
Aggregate interface
containing 3 Selected ports
666 1
Aggregate interface
containing 4 Selected ports
500 1
Configuration restrictions and guidelines
•
When it calculates path cost for an aggregate interface, IEEE 802.1t takes into account the number
of Selected ports in its aggregation group, but IEEE 802.1d-1998 does not. 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.
•
When multiple ports operate at a rate higher than 10 Gbps and the standard for default path cost
calculation is
dot1d-1998
or
legacy
, the path cost of a single port or an aggregate interface takes
the smallest value. As a result, the forwarding path selected might not be optimal. To solve this
problem, use
dot1t
as the standard for default path cost calculation, or manually set the path cost
for a port (see "
Configuring path costs of ports
").
Configuration procedure
To specify a standard for the device to use when it calculates the default path cost:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Specify a standard for the
device to use when it
calculates the default path
costs of its ports.
stp pathcost-standard
{
dot1d-1998
|
dot1t
|
legacy
}
Optional.
legacy
by default.
Configuring path costs of ports
When the path cost of a port changes, the system re-calculates the role of the port and initiates a state
transition.
To configure the path cost of ports:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter interface view or port
group view.
•
Enter Layer 2 Ethernet interface view or
Layer 2 aggregate interface view:
interface
interface-type
interface-number
•
Enter port group view:
port-group manual
port-group-name
Use one of the commands.
