Switch 7700 Command reference Guide, v2.0

342 CHAPTER 8: USING STP COMMANDS
diameter of the switching network, so that MSTP can automatically calculate and
give the moderate values for the time parameters.
Related commands: stp timer hello, stp timer max-age, stp
bridge-diameter
.
Example
Set the Forward Delay of the device to 2000 centiseconds.
[SW7700]stp timer forward-delay 2000
stp timer hello Syntax
stp timer hello centi-seconds
undo stp timer hello
View
System view
Parameter
centi-seconds: Specifies Hello Time value with an integer in the range of 100 to
1000 in units of centiseconds. By default, the Hello Time of the switch is 200
centiseconds.
Description
■ Use the stp timer hello command to configure Hello Time of the switch.
■ Use the undo stp timer hello command to restore the default Hello Time.
The STP defines to transmit configuration BPDU regularly at an interval specified
with Hello Time to keep the spanning tree stable. If the switch receives no BPDU
packets for a period of time, it will recalculate the spanning tree upon the BPDU
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 * (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 max-age, stp
bridge-diameter
.