3Com MSR 30, MSR 50 manual Stp root secondary, Stp instance instance-id root secondary

622CHAPTER 38: MSTP CONFIGURATION COMMANDS

■If you do not provide instance instance-id, your configuration will take effect in the CIST instance only.

■There is only one root bridge in effect in a spanning tree instance. If two or more devices have been designated to be root bridges of the same spanning tree instance, MSTP will select the device with the lowest MAC address as the root bridge.

■You can specify a root bridge for each MST instance without caring about the device priority. After specifying the current device as the root bridge or a secondary root bridge, you cannot change the priority of the device.

Examples # Define the current device as the root bridge of MST instance 0.

<Sysname> system-view

[Sysname] stp instance 0 root primary

stp root secondary

Syntax	stp [ instance instance-id] root secondary
	undo stp [ instance instance-id] root
View	System view
Parameters	instance instance-id: MST instance ID, in the range of 0 to 15. MST instance 0
	represents the CIST.
Description	Use the stp root secondary command to specify the current device as a
	secondary root bridge of the specified MST instance.
	Use the undo stp root command to remove the current device as a secondary
	root bridge of the specified MST instance.
	By default, a device is not a secondary root bridge.
	Note that:
	■ If you do not provide instance instance-id, your configuration will take effect
	in the CIST instance only.
	■ You can configure one or more secondary root bridges for each MST instance.
	When the root bridge of an instance fails or is shut down, the secondary root
	bridge can take over the role of the instance of the specified MST instance. If
	you specify more than one secondary root bridge, the secondary root bridge
	with the lowest Mac address will become the root bridge.
	■ Upon specifying the current device as the root bridge or a secondary root
	bridge, you cannot change the priority of the device.
Examples	# Define the current device as the secondary root bridge of MST instance 0.
	<Sysname> system-view
	[Sysname] stp instance 0 root secondary