4 Command Line Interface

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

•10 Gigabit Ethernet: 200-20,000

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

•10 Gigabit Ethernet – full duplex: 1000; trunk: 500

Command Mode

Interface Configuration (Ethernet Ports 1-8, 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 4-155)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)#

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