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3Com Switch 7750 Series
Command Reference Guide – MSTP Chapter 1
MSTP Configuration Commands
1-44
As for the configuration of the three time-related parameters (that is, the Hello time,
Forward delay, and Max age parameters), the following formulas must be met to
prevent 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 determined.
Related command: stp timer forward-delay, stp timer max-age, and stp
bridge-diameter.
Example
# Set the Hello time to 400 centiseconds.
<3Com> system-view
System View: return to User View with Ctrl+Z.
[3Com] stp timer hello 400
1.1.42 stp timer max-age
Syntax
stp timer max-age centi-seconds
undo stp timer max-age
View
System view
Parameter
centi-seconds: Max age in centiseconds to be set. This argument ranges from 600 to
4,000 and defaults to 2,000.
Description
Use the stp timer max-age command to set the Max age of the switch.
Use the undo stp timer max-age command to revert to the default Max age.
MSTP is capable of detecting link problems and automatically restoring redundant links
to forwarding state. In CIST, switches use the Max age parameter to judge whether or
not a received configuration BPDU times out. And spanning trees will be regenerated if
a configuration BPDU received by a port times out.
The Max age is meaningless to MSTIs. The Max age configured for the root bridge of
the CIST applies to all switches operating on the CIST, including the root bridge.