SPANNING
-
TREE
COST
31-17
Default Setting
By default, the system automatically detects the speed and duplex mode
used on each port, and configures the path cost according to the values
shown below. Path cost “0” is used to indicate auto-configuration
mode. When the short path cost method is select ed and the default
path cost recommended by the IEEE 8021w standard exceeds 65,535,
the default is set to 65,535.
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
• This command is used by the Spanning Tree Algorithm to determine
the best path between devices. Therefore, lower values should be
assigned to ports attached to faster media, and higher values assigned
to ports with slower media.
• Path cost takes precedence over port priority.
• When the spanning-tree pathcost method (page31-9) is set to short,
the maximum value for path cost is 65,535.
Example
Table 31-4 Default STA Path Costs
Port Type Link Type IEEE 802.1w-2001
Fast Ethernet Half Duplex
Full Duplex
Trunk
200,000
100,000
50,000
Gigabit Ethernet Full Duplex
Trunk
10,000
5,000
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree cost 50
Console(config-if)#