HP 5820X Series

78
the port can be blocked and changes to the forwarding state after a period twice the forward delay. In
the waiting period, service traffic is interrupted.
Among loop guard, root guard and edge port settings, only one function (whichever is configured the
earliest) can take effect on a port at the same time.
Configuring path costs of ports
CAUTION:
If you change the standard that the device uses in calculating the default path costs, you restore the
path costs to the default. Also, when the path cost of a port changes, MSTP re-calculates the role of the
port and initiates a state transition.
Path cost is a parameter related to the rate of a port. On an MSTP-enabled 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.
The device can automatically calculate the default path cost; alternatively, you can also configure the path
cost for ports.
Make the following configurations on the leaf nodes only.
Specifying a standard that the device uses when calculating the default path cost
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.
To specify a standard for the device to use when calculating the default path cost:
To do... Use the command... Remarks
1. Enter system view
system-view —
2. Specify a standard for the
device to use when
calculating the default path
costs of its ports
stp pathcost-standard { dot1d-
1998 | dot1t | legacy }
Optional.
By default, the device calculates
the default path cost for ports
based on a private standard.
Table 15 shows the mappings between the link speed and the path cost.
Table 15 Mappings between the link speed and the path cost
Path cost
Link speed Port type
IEEE 802.1d-1998 IEEE 802.1t Private standard
0 — 65,535 200,000,000 200,000
Single Port 2,000,000 2000
Aggregate interface
containing 2 selected ports
1,000,000 1800
10 Mbps
Aggregate interface
containing 3 selected ports
100
666,666 1600