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Spanning Tree Commands
4-171
4
The recommended range is:
•Ethernet: 200,000-20,000,000
•Fast Ethernet: 20,000-2,000,000
•Gigabit Ethernet: 2,000-200,000
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 selected and the default path cost recommended by
the IEEE 8021w standard exceeds 65,535, the default is set to 65,535.
• Ethernet – half duplex: 2,000,000; full duplex: 1,000,000; trunk: 500,000
• Fast Ethernet – half duplex: 200,000; full duplex: 100,000; trunk: 50,000
• Gigabit Ethernet – full duplex: 10,000; trunk: 5,000
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 (page 4-165) is set to short, the
maximum value for path cost is 65,535.
Example
spanning-tree port-priority
This command configures the priority for the specified interface. Use the no form to
restore the default.
Syntax
spanning-tree port-priority priority
no spanning-tree port-priority
priority - The priority for a port. (Range: 0-240, in steps of 16)
Default Setting
128
Command Mode
Interface Configuration (Ethernet, Port Channel)
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree cost 50
Console(config-if)#