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Spanning Tree Commands
51-12
51
spanning-tree cost
This command configures the spanning tree path cost for the specified interface.
Use the no form to restore the default.
Syntax
spanning-tree cost cost
no spanning-tree cost
cost - The path cost for the port.
(Range: 0 for auto-configuration, or 1-200,000,000)
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.
• 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 51-6) is set to short, the
maximum value for path cost is 65,535.
Example
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree cost 50
Console(config-if)#