Cisco 2950 Software Configuration Guide - Page 313
Configuring the Path Cost
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Chapter 14 Configuring STP Configuring Spanning-Tree Features Configuring the Path Cost The spanning-tree path cost default value is derived from the media speed of an interface. If a loop occurs, spanning tree uses cost when selecting an interface to put in the forwarding state. You can assign lower cost values to interfaces that you want selected first and higher cost values that you want selected last. If all interfaces have the same cost value, spanning tree puts the interface with the lowest interface number in the forwarding state and blocks the other interfaces. Beginning in privileged EXEC mode, follow these steps to configure the cost of an interface. This procedure is optional. Step 1 Step 2 Command configure terminal interface interface-id Step 3 spanning-tree cost cost Step 4 spanning-tree vlan vlan-id cost cost Step 5 Step 6 Step 7 end show spanning-tree interface interface-id or show spanning-tree vlan vlan-id copy running-config startup-config Purpose Enter global configuration mode. Specify an interface to configure, and enter interface configuration mode. Valid interfaces include physical interfaces and port-channel logical interfaces (port-channel port-channel-number). Configure the cost for an interface. If a loop occurs, spanning tree uses the path cost when selecting an interface to place into the forwarding state. A lower path cost represents higher-speed transmission. For cost, the range is 1 to 200000000; the default value is derived from the media speed of the interface. Configure the cost for a VLAN. If a loop occurs, spanning tree uses the path cost when selecting an interface to place into the forwarding state. A lower path cost represents higher-speed transmission. • For vlan-id, you can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma. The range is 1 to 1005 when the SI is installed and 1 to 4094 when the EI is installed. • For cost, the range is 1 to 200000000; the default value is derived from the media speed of the interface. Return to privileged EXEC mode. Verify your entries. (Optional) Save your entries in the configuration file. Note The show spanning-tree interface interface-id privileged EXEC command displays information only for ports that are in a link-up operative state. Otherwise, you can use the show running-config privileged EXEC command to confirm the configuration. 78-11380-10 Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide 14-19
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