Cisco Systems 3750E Spanning-tree vlan vlan-id root primary, Show spanning-tree detail, 18-17

Chapter 18 Configuring STP

Configuring Spanning-Tree Features

Note The root switch for each spanning-tree instance should be a backbone or distribution switch. Do not configure an access switch as the spanning-tree primary root.

Use the diameter keyword to specify the Layer 2 network diameter (that is, the maximum number of switch hops between any two end stations in the Layer 2 network). When you specify the network diameter, the switch automatically sets an optimal hello time, forward-delay time, and maximum-age time for a network of that diameter, which can significantly reduce the convergence time. You can use the hello keyword to override the automatically calculated hello time.

Note After configuring the switch as the root switch, we recommend that you avoid manually configuring the hello time, forward-delay time, and maximum-age time through the spanning-tree vlan vlan-idhello-time, spanning-tree vlan vlan-idforward-time, and the spanning-tree vlan vlan-idmax-ageglobal configuration commands.

Beginning in privileged EXEC mode, follow these steps to configure a switch to become the root for the specified VLAN. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	spanning-tree vlan vlan-idroot primary	Configure a switch to become the root for the specified VLAN.
	[diameter net-diameter[hello-time seconds]]	• 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 4094.
		• (Optional) For diameter net-diameter, specify the
		maximum number of switches between any two end
		stations. The range is 2 to 7.
		• (Optional) For hello-timeseconds, specify the interval in
		seconds between the generation of configuration messages
		by the root switch. The range is 1 to 10; the default is 2.
Step 3
	end	Return to privileged EXEC mode.
Step 4
	show spanning-tree detail	Verify your entries.
Step 5
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To return to the default setting, use the no spanning-tree vlan vlan-idroot global configuration command.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		18-17