3Com 10014298 manual Specify the Switch as Primary or Secondary Root Switch

192CHAPTER 8: STP OPERATION

You can use the following commands to specify the current switch as the primary or secondary root of the spanning tree.

Perform the following configuration in system view.

Table 192 Specify the Switch as Primary or Secondary Root Switch

Operation	Command
Specify current switch as the primary root	stp instance instance-idroot
switch of the specified spanning tree.	primary [	bridge-diameter
	bridgenum	[ hello-time
	centi-senconds ] ]

Specify current switch as the secondary root switch of the specified spanning tree.

stp instance instance-idroot secondary [ bridge-diameter bridgenum [ hello-time centi-senconds ] ]

Specify current switch not to be the primary or	undo stp instance instance-id
secondary root.	root

After a switch is configured as primary root switch or secondary root switch, you cannot modify the bridge priority of the switch.

You can configure the current switch as the primary or secondary root switch of the STI (specified by the instance instance-idparameter). If the instance-idtakes 0, the current switch is specified as the primary or secondary root switch of the CIST.

The root types of a switch in different STIs are independent of one another. A switch can be a primary or secondary root of any STI. However, a switch cannot serve as both the primary and secondary roots of one STI.

If the primary root is down or powered off, unless you configure a new primary root, the secondary root will take its place. If there are two or more configured secondary root switches, MSTP selects the one with the smallest MAC address to take the place of the failed primary root.

When configuring the primary and secondary switches, you can also configure the network diameter and hello time of the specified switching network. For detailed information, refer to the configuration tasks “Configuring the Switching Network Diameter” and “Configuring the Time Parameters of a Switch”.

You can configure the current switch as the root of several STIs, however, it is not necessary to specify two or more roots for an STI. In other words, please do not specify the root for an STI on two or more switches.

You can configure more than one secondary root for a spanning tree by specifying the secondary STI root on two or more switches.

Generally, you are recommended to designate one primary root and more than one secondary root for a spanning tree.

By default, a switch is neither the primary root or the secondary root of the spanning tree.

Configuring the MSTP MSTP and RSTP are compatible and can recognize each other’s packets. However, Running Mode STP cannot recognize MSTP packets. To implement the compatibility, MSTP