Filter
Top Products
200 CHAPTER 8: STP OPERATION
In calculating the path cost of aggregation links, the 802.1D-1998 does not take
into account the number of aggregation links, but the 802.1T does. The formula
involved is:
Path Cost = 200,000,000/link speed in 100Kbps
Where the link speed is the sum of the speed of the ports in unblocked status
within the aggregation links.
Configuring the Priority
of a Port
For spanning tree calculation, the port priority is an important factor when
determining if a port can be elected as the root port. With other attributes 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 play different roles.
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.
Configuring in Ethernet Port View
Perform the following configuration in Ethernet port view.
For more about the commands, see the Switch 7750 Command Reference Guide.
After the change of port priority, MSTP will recalculate the port role and transit the
state. 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 with actual
networking requirements.
By default, the priority of all the Ethernet ports is 128.
Table 206 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
Table 207 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