1-43You can specify the current switch as the root bridge of an MSTI regardless of the priority of the switch.You can also specify the network diameter of the switched network by using the stp root primarycommand. The switch will then figure out the following three time parameters: hello time, forward delay,and max age. As the hello time figured out by the network diameter is not always the optimal one, youcan set it manually through the hello-time centi-seconds parameter. Generally, you are recommendedto obtain the forward delay and max age parameters through setting the network diameter.z You can configure only one root bridge for an MSTI and can configure one or more secondary rootbridges for an MSTI. Specifying multiple root bridges for an MSTI causes unpredictable spanningtree calculation results.z Once a switch is configured as the root bridge or a secondary root bridge, its priority cannot bemodified.Examples# Configure the current switch as the root bridge of MSTI 1, set the network diameter of the switchednetwork to 4, and set the hello time to 500 centiseconds. system-viewSystem View: return to User View with Ctrl+Z.[Sysname] stp instance 1 root primary bridge-diameter 4 hello-time 500stp root secondarySyntaxstp [ instance instance-id ] root secondary [ bridge-diameter bridgenum [ hello-timecenti-seconds ] ]undo stp [ instance instance-id ] rootViewSystem viewParametersinstance-id: MSTI ID ranging from 0 to 16. The value of 0 refers to the CIST.bridgenum: Network diameter of the specified spanning tree. This argument ranges from 2 to 7 anddefaults to 7.centi-seconds: Hello time in centiseconds of the specified spanning tree. This argument ranges from100 to 1,000 and defaults to 200.DescriptionUse the stp root secondary command to configure the current switch as a secondary root bridge of aspecified MSTI.Use the undo stp root command to cancel the current configuration.
