Cisco Systems N3KC3064TFAL3 Configuring the Root Bridge, synchronize, Procedure, Purpose, Step

Configuring Multiple Spanning Tree

Configuring the Root Bridge

Procedure

	Command or Action	Purpose
Step 1	switch# configure terminal	Enters configuration mode.
Step 2	switch(config)# spanning-tree mst	Enters MST configuration submode.
	configuration
Step 3	switch(config-mst)# private-vlan	Automatically maps all secondary VLANs to the
	synchronize	same MSTI and their associated primary VLAN
		for all private VLANs.

This example shows how to automatically map all the secondary VLANs to the same MSTI as their associated primary VLANs in all private VLANs:

switch# configure terminal

switch(config)# spanning-tree mst configuration switch(config-mst)#private-vlan synchronize

Configuring the Root Bridge

You can configure the switch to become the root bridge.

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

Enter the diameter keyword, which is available only for MSTI 0 (or the IST), to specify the network diameter (that is, the maximum number of hops between any two end stations in the 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 enter the hello keyword to override the automatically calculated hello time.

Note With the switch configured as the root bridge, do not manually configure the hello time, forward-delay time, and maximum-age time using the spanning-tree mst hello-time, spanning-tree mst forward-time, and spanning-tree mst max-ageglobal configuration commands.

Procedure

	Command or Action	Purpose
Step 1	switch# configure terminal	Enters configuration mode.
Step 2	switch(config)# spanning-tree	Configures a switch as the root bridge as follows:
	mst instance-idroot {primary

Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)

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