3com 8807 Reference Guide

C

HAPTER

 13: MSTP C

ONFIGURATION

 C

OMMANDS

timeouts. The 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.

# Set Hello Time of the switch to 400 centiseconds.

<SW8800>system-view

 

System View: return to User View with Ctrl+Z

 

[SW8800] stp timer hello 400 

stp timer max-age centi-senconds

System view

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.

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 the port expires according to the Max Age. If the BPDU expires, the 
MSTI has to be calculated again.

Max Age takes no effect on MSTIs. If the current switch is CIST root bridge, it will 
check if the configuration BPDU expires according to the configured Max Age. 
Otherwise, the switch adopts the Max Age configured on the CIST root bridge.