R2511-HP MSR Router Series Layer 2 - LAN Switching Command Reference(V5)

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Default
The device automatically calculates the path costs of ports in each spanning tree based on the
corresponding standard.
Views
Ethernet interface view, port group view, Layer 2 aggregate interface view
Default command level
2: System level
Parameters
instance instance-id: Sets the path cost of the ports in a particular MSTI. The minimum value of instance-id
is 0, representing the CIST, and the maximum value of instance-id is 15.
cost: Specifies the path cost of the port, with an effective range that depends on the path cost calculation
standard adopted.
• With the IEEE 802.1d-1998 standard selected for path cost calculation, the value range for the cost
argument is 1 to 65535.
• With the IEEE 802.1t standard selected for path cost calculation, the value range for the cost
argument is 1 to 200000000.
• With the private standard selected for path cost calculation, the value range for the cost argument
is 1 to 200000.
Usage guidelines
Configured in Ethernet interface view, the setting takes effect only on the interface.
Configured in port group view, the setting takes effect on all member ports in the port group.
Configured in Layer 2 aggregate interface view, the setting takes effect only on the aggregate interface.
Configured on a member port in an aggregation group, the setting takes effect only after the port leaves
the aggregation group.
To set the path cost of an MSTP port in a specific MSTI, use this command with the MSTI specified.
Path cost is an important factor in spanning tree calculation. Setting different path costs for a port in
MSTIs allows different VLAN traffic flows to be forwarded along different physical links and enables
VLAN-based load balancing.
The path cost setting of a port can affect the role selection of the port. When the path cost of a port is
changed, the system re-calculates the role of the port and initiates a state transition.
The following matrix shows the command and router compatibility:
Command MSR900 MSR93
X
MSR20-1
X
MSR20 MSR30 MSR50 MSR1000
stp cost (Layer 2
aggregate
interface view)
No Yes No No Yes Yes Yes
Examples
# In MSTP mode, set the path cost of port Ethernet 1/3 in MSTI 2 to 200.
<Sysname> system-view
[Sysname] interface ethernet 1/3
[Sysname-Ethernet1/3] stp instance 2 cost 200