Command Manual – STP 
Quidway S8500 Series Routing Switches  Chapter 1  
MSTP Configuration Commands
 
Huawei Technologies Proprietary 
1-17 
1.1.16  stp instance root primary 
Syntax 
stp  [ instance instance-id ] root primary [ bridge-diameter bridgenum [ hello-time 
centi-senconds ] ] 
undo stp  [ instance instance-id ] root 
View 
System view 
Parameter 
instance-id: Specifies the spanning tree instance ID, ranging from 0 to 48. Specify it as 
0 to configure the root bridge of CIST.  
root primary: Configures the current switch as the primary root of the specified MSTI.  
bridge-diameter bridgenum: Specifies the network diameter of the spanning tree, 
ranging from 2 to 7.  
hello-time centi-senconds: Specifies the Hello Time of the spanning tree, which is in 
the range from 100 to 1000 and measured in centiseconds.  
Description 
Use the stp root primary command to configure the current switch as the primary root 
of the specified MSTI. 
Use the undo stp root command to cancel the current switch for the primary root of the 
designated MSTI. 
If you execute these commands without using the instance instance-id option, your 
configuration takes effect only on the CIST instance. 
When you set the instance-id parameter to 0, its following parameter setting takes 
effect. 
By default, the switch does not server as a root bridge.  
You can specify one root bridge for each MSTI regardless of the switch priority. When 
setting a root bridge, you can use this command to specify the switching network 
diameter and determine the three time parameters (Hello time, Forward Delay and Max 
Age). Because the switch calculates inaccurate Hello time value, you can specify the 
switching network diameter and the Hello Time for the root bridge, and thus determine 
other two parameter values for the root bridge. In general, you are recommended to 
determine the other two time parameter values by setting the network diameter.