H3C S6850 Series, Руководство по настройке

Страница: 307 / 394

38
Link speed Port type
Path cost
IEEE
802.1d-1998
IEEE 802.1t
Private
standard
Aggregate interface
containing two Selected
ports
100 1
Aggregate interface
containing three Selected
ports
66 1
Aggregate interface
containing four Selected
ports
50 1
Restrictions and guidelines
If you change the standard for the default path cost calculation, you restore the path costs to the
default.
When the device calculates the path cost for an aggregate interface, IEEE 802.1t takes into account
the number of Selected ports in its aggregation group. However, IEEE 802.1d-1998 does not take
into account the number of Selected ports. The calculation formula of IEEE 802.1t is: Path cost =
200,000,000/link speed (in 100 kbps). The link speed is the sum of the link speed values of the
Selected ports in the aggregation group.
IEEE 802.1d-1998 or the private standard always assigns the smallest possible value to a single port
or aggregate interface with a speed exceeding 10 Gbps. The forwarding path selected based on this
criterion might not be the best one. To solve this problem, perform one of the following tasks:
•
Use
dot1t
as the standard for default path cost calculation.
•
Manually set the path cost for the port (see " Configuring path costs of ports ").
Procedure
1.
Enter system view.
system-view
2.
Specify a standard for the default path costs calculation.
stp pathcost-standard { dot1d-1998 | dot1t | legacy }
By default, the device uses
legacy
to calculate the default path costs of its ports.
Configuring path costs of ports
Restrictions and guidelines
When the path cost of a port changes, the system recalculates the port role and initiates a state
transition.
Procedure
1.
Enter system view.
system-view
2.
Enter interface view.
interface interface-type interface-number
3.
Configure the path cost of the ports.
{
In STP/RSTP mode:
stp cost cost-value