170 CHAPTER 14: MSTP CONFIGURATION
whereas the 802.1T standard does. The following formula is used to calculate the
path cost of an aggregated link:
Path cost = 200,000/ link transmission speed,
where ‘link transmission speed" is the sum of the speeds of all the unblocked
ports on the aggregated link measured in 100 Kbps.
Configure the path cost for specific ports
Changing the path cost of a port may change the role of the port and put it in
state transition. Executing the stp cost command with the instance-id argument
being 0 sets the path cost on the CIST for the port.
n
The range of the path cost of an Ethernet port varies by the standard used for path
cost calculation as follows:
■ With the IEEE 802.1d-1998 standard adopted, the path cost ranges from 1 to
65535.
■ With the IEEE 802.1t standard adopted, the path cost ranges from 1 to
200000000.
■ With the proprietary standard adopted, the path cost ranges from 1 to
200000.
Configuration example (A)
# Configure the path cost of Ethernet 1/0/1 in spanning tree instance 1 to be
2,000.
1 Perform this configuration in system view
<4210> system-view
[4210] stp interface Ethernet1/0/1 instance 1 cost 2000
2 Perform this configuration in Ethernet port view
Tabl e 124 Configure the path cost for specified ports in system view
Operation Command Description
Enter system view System-view -
Configure the path cost for
specified ports
stp interface interface-list [
instance instance-id ] cost
cost
Required
An MSTP-enabled switch can
calculate path costs for all its
ports automatically.
Tabl e 125 Configure the path cost for a port in Ethernet port view
Operation Command Description
Enter system view System-view -
Enter Ethernet port view interface interface-type
interface-number
-
Configure the path cost for
the port
stp [ instance instance-id ]
cost cost
Required
A MSTP-enabled switch can
calculate path costs for all its
ports automatically.
To Next Page
Loading...
