H3C S7500 Series Operation Manual page 271

Operation Manual – MSTP
H3C S7500 Series Ethernet Switches
Normally, the path cost of a port operating in full-duplex mode is slightly less than that of
the port operating in half-duplex mode.
When calculating the path cost of an aggregated link, the 802.1D-1998 standard does
not take the number of the ports on the aggregated link into account, whereas the
802.1T standard does. The following formula is used to calculate the path cost of an
aggregated link:
Path cost = 200,000,000/ link transmission speed (in 100 kbps),
Where the link transmission speed is the sum of the speeds of the unblocked ports on
the aggregated link, which is measured in 100 Kbps.
II. Configuring the path costs of ports
Follow these steps to configure the path cost for specified ports in system view:
To do ...
Enter system view
Configure the path
cost for specified
ports
Follow these steps to configure the path cost for a port in Ethernet port view:
To do ...
Enter system view
Enter Ethernet port
view
Configure the path
cost for the port
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.
III. Configuration example (A)
# Configure the path cost of Ethernet2/0/1 in MSTI 1 to be 2,000.
1) Configure in system view.
<H3C> system-view
[H3C] stp interface ethernet2/0/1 instance 1 cost 2000
2) Configure in Ethernet port view.
Use the command ...
system-view
stp interface interface-list
[ instance instance-id ] cost
cost
Use the command ...
system-view
interface interface-type
interface-number
stp [ instance instance-id ]
cost cost
1-27
Chapter 1 MSTP Configuration
Remarks
—
Required
An MSTP-enabled switch can
calculate path costs for all its
ports automatically.
Remarks
—
—
Required
An MSTP-enabled switch can
calculate path costs for all its
ports automatically.