Command Manual – STP 
Quidway S8500 Series Routing Switches  Chapter 1  
MSTP Configuration Commands
 
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root bridge transmits BPDU packets at an interval as you configured, while other 
switches apply the Hello Time configured on the root bridge.  
When configuring Hello time, Forward Delay and Max Age, remember to guarantee the 
following equations:  
2 x (Forward Delay -1.0 second) >= Max Age 
Max Age >= 2 x (Hello Time + 1.0 second) 
Only if the earlier-mentioned formulas are equal can the MSTP normally operate on the 
entire network. Otherwise, the network may flap frequently. You are recommended to 
use the stp bridge-diameter command to specify the diameter of the switching 
network, so that MSTP can automatically calculate and give the moderate values for 
the time parameters. 
Related command: stp timer forward-delay,  stp timer max-age,  stp 
bridge-diameter. 
Example 
# Set Hello Time of the switch to 400 centiseconds. 
<Quidway>system-view 
System View: return to User View with Ctrl+Z  
[Quidway] stp timer hello 400 
1.1.40  stp timer max-age 
Syntax 
stp timer max-age centi-senconds 
undo stp timer max-age 
View 
System view 
Parameter 
centi-seconds: Specifies the Max Age, which is in the range from 600 to 4000 and 
measured with centiseconds. By default, the Max Age of the switch is 2000 
centiseconds. 
Description 
Use the stp timer max-age command to configure the Max Age of the switch. 
Use the undo stp timer max-age command to restore the default Max Age. 
MSTP can detect the link fault and automatically resume the forwarding state of the 
redundant link. On the CIST, the switch checks if the configuration BPDU received via