Switch 7700 Command reference Guide, v2.0

MSTP Configuration Commands 343
Example
Set Hello Time of the switch 300 centiseconds.
[SW7700]stp timer hello 300
stp timer max-age Syntax
stp timer max-age centi-seconds
undo stp timer max-age
View
System view
Parameter
centiseconds: Specifies the Max Age, ranging 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 the port expires according to the Max Age. If the BPDU expires, the STI
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.
When you configure Hello time, Forward Delay and Max Age, ensure the following
formulas equal:
2 * (Forward Delay -1.0 seconds) >= Max Age
Max Age >= 2 * (Hello Time + 1.0 seconds)
Only if the above-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 instance root primary 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 commands: stp timer forward-delay, stp timer hello, stp
bridge-diameter
.
Example
Set Max Age of the device to 1000 centiseconds.
[SW7700]stp timer max-age 1000