Configuring Port Priority - 3Com S7906E Configuration 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.
Configuration example
# Specify that the device use 802.1d-1998 when calculating the default path costs of its ports.
<Sysname> system-view
[Sysname] stp pathcost-standard dot1d-1998
# Set the path cost of GigabitEthernet 2/0/3 on MSTI 2 to 200.
<Sysname> system-view
[Sysname] interface gigabitethernet 2/0/3
[Sysname-GigabitEthernet2/0/3] stp instance 2 cost 200

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.
Make this configuration on the leaf nodes only.
Follow these steps to configure the priority of a port or a group of ports:
Enter system view
Enter
interface view
or port group
view
Configure the port priority
To do...
Enter Ethernet interface
view, or Layer 2
aggregate interface
view
Enter port group view
Use the command...
system-view
interface interface-type
interface-number
port-group manual
port-group-name
stp [ instance
instance-id ] port priority
priority
1-26
Remarks
—
Required
Use either command.
Optional
128 for all ports by default.