Configuring path costs of ports – H3C Technologies H3C S5560 Series Switches User Manual
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Step Command Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Layer 2 Ethernet or
aggregate interface view.
interface interface-type interface-number
N/A
3.
Configure the current ports as
edge ports.
stp edged-port
By default, all ports are
non-edge ports.
Configuring path costs of ports
Path cost is a parameter related to the rate of a port. On a spanning tree device, a port can have different
path costs in different MSTIs. Setting appropriate path costs allows VLAN traffic flows to be forwarded
along different physical links, achieving VLAN-based load balancing.
You can have the device automatically calculate the default path cost, or you can configure the path cost
for ports.
Specifying a standard for the device to use when it calculates
the default path cost
CAUTION:
If you change the standard that the device uses to calculate the default path costs, you restore the path
costs to the default.
You can specify a standard for the device to use in automatic calculation for the default path cost. The
device supports the following standards:
•
dot1d-1998—The device calculates the default path cost for ports based on IEEE 802.1d-1998.
•
dot1t—The device calculates the default path cost for ports based on IEEE 802.1t.
•
legacy—The device calculates the default path cost for ports based on a private standard.
When you specify a standard for the device to use when it calculates the default path cost, follow these
guidelines:
•
When it 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), where 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 an aggregate interface when the link speed of the port or interface exceeds 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
").
To specify a standard for the device to use when it calculates the default path cost: