H3C S7500 Series Ethernet Switches Operation Manual

Operation Manual – MSTP
H3C S7500 Series Ethernet Switches Chapter 1
MSTP Configuration
1-27
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 ... Use the command ... Remarks
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.
Follow these steps to configure the path cost for a port in Ethernet port view:
To do ... Use the command ... Remarks
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
An MSTP-enabled switch can
calculate path costs for all its
ports automatically.
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.