3com 5500-ei pwr Reference Guide

 

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centi-seconds: Hello time to be set, in the range of 100 to 1,000 (in centiseconds). 

Use the stp timer hello command to set the hello time of the switch. 

Use the undo stp timer hello command to restore the hello time of the switch to the default value. 

By default, the hello time of the switch is 200 centiseconds. 

A root bridge regularly sends out configuration BPDUs to maintain the stability of existing spanning 

trees. If the switch does not receive BPDU packets in a specified period, spanning trees will be 

recalculated because BPDU packets time out. When a switch becomes a root bridge, it regularly sends 

BPDUs at the interval specified by the hello time you have configured on it. The other none-root-bridge 

switches adopt the interval specified by the hello time.  

As for the configuration of the three time-related parameters (namely, the hello time, forward delay, and 

max age parameters), the following formulas must be met to prevent frequent network jitter. 

2 × (forward delay – 1 second) >= max age 

Max age >= 2 × (hello time + 1 second) 

You are recommended to specify the network diameter of the switched network and the hello time by 

using the stp root primary or stp root secondary command. After that, the three proper time-related 

parameters are automatically calculated by MSTP. 

Related commands: stp timer forward-delay, stp timer max-age, stp bridge-diameter. 

# Set the hello time to 400 centiseconds. 

<Sysname> system-view  

System View: return to User View with Ctrl+Z. 

[Sysname] stp timer hello 400 

stp timer max-age centi-seconds 

undo stp timer max-age 

System view 

centi-seconds: Max age to be set, in the range of 600 to 4,000 (in centiseconds). 

Use the stp timer max-age command to set the max age of the switch. 

Use the undo stp timer max-age command to restore the default max age. 

By default, the max age of a switch is 2,000 centiseconds.