Configuring Port Priority - H3C S5120-EI Series Operation Manual

If you change the standard that the device uses in calculating the default path cost, the port path
cost value set through the stp cost command will be invalid.
When the path cost of a port is changed, MSTP will re-calculate the role of the port and initiate a
state transition. If you use 0 as instance-id, you are setting the path cost of the CIST.

Configuring Port Priority

The priority of a port is an important factor in determining whether the port can be elected as the root
port of a device. If all other conditions are the same, the port with the highest priority will be elected as
the root port.
On an MSTP-enabled device, a port can have different priorities in different MSTIs, and the same port
can play different roles in different MSTIs, so that data of different VLANs can be propagated along
different physical paths, thus implementing per-VLAN load balancing. You can set port priority values
based on the actual networking requirements.
Configuration procedure
Follow these steps to configure the priority of a port or a group of ports:
To do...
Enter system view
Enter
interface view
or port group
view
Configure a priority for the
port(s)
When the priority of a port is changed, MSTP will re-calculate the role of the port and initiate a state
transition.
Generally, a lower configured value indicates a higher priority. If you configure the same priority
value for all the ports on a device, the specific priority of a port depends on the index number of the
port. Changing the priority of a port triggers a new spanning tree calculation process.
Use the command...
system-view
Enter Ethernet
interface view
interface interface-type
or Layer-2
interface-number
aggregate
interface view
Enter port
port-group manual
group view
port-group-name
stp [ instance instance-id ]
port priority priority
1-30
Remarks
—
Required
Use either command.
Configurations made in
interface view will take effect on
the current port only;
configurations made in port
group view will take effect on all
ports in the port group.
Optional
128 for all Ethernet ports by
default.