3Com 7700 Configuration Manual page 241

Configuring the Priority
of a Port
Configuring in System View
Perform the following configuration in system view.
Table 31 Configure the Path Cost of a Port
Operation
Configure the Path Cost of a port.
Restore the default path cost of a port.
Configuring in Ethernet Port View
Perform the following configuration in Ethernet port view.
Table 32 Configure the Path Cost of a Port
Operation
Configure the Path Cost of a port
Restore the default path cost of a port.
For more about the commands, see the Switch 7700 Command Reference Guide.
Upon the change of path cost of a port, MSTP will recalculate the port role and
transit the state. When instance-id takes 0, it indicates to set the path cost on the
CIST.
By default, MSTP is responsible for calculating the port path cost.
For spanning tree calculation, the port priority is an importance factor to
determine if a port can be elected as the root port. With other things being equal,
the port with the highest priority is elected as the root port. On the MSTP switch, a
port can have different priorities in different STIs and plays different roles. Thus,
the traffic from different VLANs can run over different physical links, thereby
implementing the VLAN-based load-balancing.
You can configure the port priority in the following ways.
Configuring in System View
Perform the following configuration in system view.
Table 33 Configure the Port Priority
Operation
Configure the port priority.
Restore the default port priority.
Configuring in Ethernet Port View
Perform the following configuration in Ethernet port view.
Table 34 Configure the Port Priority
Operation
Configure the port priority.
Configuring MSTP
Command
stp interface interface-list instance
instance-id cost cost
undo stp interface interface-list instance
instance-id cost
Command
stp instance instance-id cost cost
undo stp instance instance-id cost
Command
stp interface interface-list instance
instance-id port priority priority
undo stp interface interface-list instance
instance-id port priority
Command
stp instance instance-id port priority priority
233