Operation Manual – MSTPH3C S5600 Series Ethernet Switches Chapter 1 MSTP Configuration1-23same MSTI, a switch cannot be the root bridge and the secondary root bridgesimultaneously.When the root bridge fails or is turned off, the secondary root bridge becomes the rootbridge if no new root bridge is configured. If you configure multiple secondary rootbridges for an MSTI, the one with the smallest MAC address replaces the root bridgewhen the latter fails.You can specify the network diameter and the hello time parameters while configuring aroot bridge/secondary root bridge. Refer to Configuring the Network Diameter of theSwitched Network and Configuring the MSTP Time-related Parameters for informationabout the network diameter parameter and the hello time parameter.Note:z You can configure a switch as the root bridges of multiple MSTIs. But you cannotconfigure two or more root bridges for one MSTI. So, do not configure root bridgesfor the same MSTI on two or more switches using the stp root primary command.z You can configure multiple secondary root bridges for one MSTI. That is, you canconfigure secondary root bridges for the same MSTI on two or more switches usingthe stp root secondary command.z You can also configure the current switch as the root bridge by setting the priority ofthe switch to 0. Note that once a switch is configured as the root bridge or asecondary root bridge, its priority cannot be modified.III. Configuration example# Configure the current switch as the root bridge of MSTI 1 and a secondary root bridgeof MSTI 2. system-view[Sysname] stp instance 1 root primary[Sysname] stp instance 2 root secondary1.3.4 Configuring the Bridge Priority of the Current SwitchRoot bridges are selected according to the bridge priorities of switches. You can makea specific switch be selected as a root bridge by setting a lower bridge priority for theswitch. An MSTP-enabled switch can have different bridge priorities in different MSTIs.I. Configuration procedureFollow these steps to configure the bridge priority of the current switch:
