3Com Switch 8800 Family Configuration Guide

144 CHAPTER 17: MSTP REGION-CONFIGURATION
By default, the switch calculates the default path cost of a port by the legacy
standard.
Configuring the Priority
of a Port
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 will be elected as the root port. On the MSTP
switch, a port can have different priorities in different STIs and plays different roles
respectively. 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.
Configuration in system view
Perform the following configuration in system view.
Configuration in Ethernet port view
Perform the following configuration in Ethernet port view.
You can configure the port priority with either of the earlier-mentioned measures.
Upon the change of port priority, MSTP will recalculate the port role and transit
the state. Generally, a smaller value represents a higher priority. If all the Ethernet
ports of a switch are configured with the same priority value, the priorities of the
ports will be differentiated by the index number. The change of Ethernet port
priority will lead to spanning tree recalculation. You can configure the port priority
according to actual networking requirements.
By default, the priority of all the Ethernet ports is 128.
Configuring the Port
(Not) to Connect with
the Point-to-Point Link
The point-to-point link directly connects two switches.
You can configure the port (not) to connect with the point-to-point link in the
following ways.
Tabl e 123 Specifying the standard to be followed in path cost calculation
Operation Command
Specify the standard to be adopted when the
switch calculates the default path cost for the
connected link
stp pathcost-standard { dot1d-1998 | dot1t
legacy}
Restore the default standard to be used undo stp pathcost-standard
Tabl e 124 Configure the port priority
Operation Command
Configure the port priority
stp interface interface-list instance
instance-id port priority priority
Restore the default port priority
undo stp interface interface-list instance
instance-id port priority
Tabl e 125 Configure the port priority
Operation Command
Configure the port priority stp [ instance instance-id ] port priority priority
Restore the default port priority undo stp [ instance instance-id ] port priority