Configuring Path Costs Of Ports; Configuration Example - HP 3100 Series Configuration Manual

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
Configuration procedure
To specify a standard for the device to use when it calculates the default path cost:
Step
Enter system view.
1.
Specify a standard for the
2.
device to use when it
calculates the default path
costs of its ports.

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
Enter system view.
1.
Enter interface view or port
2.
group view.
Configure the path cost of
3.
the ports.

Configuration example

# In MSTP mode, specify the device to calculate the default path costs of its ports by using IEEE
802.1d-1998, and set the path cost of Ethernet 1/0/3 to 200 on MSTI 2.
<Sysname> system-view
[Sysname] stp pathcost-standard dot1d-1998
[Sysname] interface ethernet 1/0/3
[Sysname-Ethernet1/0/3] stp instance 2 cost 200
(Configuring path costs of
Command
system-view
stp pathcost-standard
{ dot1d-1998 | dot1t | legacy }
Command
system-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
•
In STP/RSTP mode:
stp cost cost
•
In PVST mode:
stp vlan vlan-list cost cost
•
In MSTP mode:
stp [ instance instance-id ] cost
cost
74
ports).
Remarks
N/A
Optional.
legacy by default.
Remarks
N/A
Use one of the commands.
Use one of the commands.
By default, the system
automatically calculates
the path cost of each port.