3Com Switch 8800 Configuration Guide Chapter 38 MSTP Region-configuration
38-26
The rate of the primary port in an aggregation group is determined by the sum of the
port rates in this group. No calculation is performed for secondary port.
z Non-aggregation port
The actual rate counts, but the rate is 0 if the port is down.
2) Calculating the path cost
Table 38-18 details the correspondence between the rate range and the value range of
the path cost of the ports.
Table 38-18 Correspondence between the rate range and path cost range
Rate range Path cost range
[0, 100] 2200 to (20 × rate)
(100,1000] 220 to the integer of [(0.2 × rate)]
(1000,10000] 22 to the integer of [(0.002 × rate)]
> 10000 1
You can specify the intended standard by using the following commands.
Perform the following configuration in system view.
Table 38-19 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
By default, the switch calculates the default path cost of a port by the DOT1T standard.
38.2.13 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.
I. Configuration in system view
Perform the following configuration in system view.