Stp Timer Hello - 3Com Switch 4500 Family Manual

Description
Use the stp timer forward-delay command to set the forward delay of the switch.
Use the undo stp timer forward-delay command to restore the forward delay to the default value.
By default, the forward delay of the switch is 1,500 centiseconds.
To prevent the occurrence of temporary loops, when a port changes its state from discarding to
forwarding, it undergoes an intermediate state and waits for a specific period to synchronize with the
state transition of the remote switches. This state transition period is determined by the forward delay
configured on the root bridge.
The forward delay setting configured on a root bridge applies to all non-root bridges.
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 x (forward delay – 1 second) >= max age
Max age >= 2 x (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 hello, stp timer max-age, stp bridge-diameter.
Examples
# Set the forward delay to 2,000 centiseconds.
<Sysname> system-view
System View: return to User View with Ctrl+Z.
[Sysname] stp timer forward-delay 2000

stp timer hello

Syntax
stp timer hello centi-seconds
undo stp timer hello
View
System view
Parameters
centi-seconds: Hello time to be set, in the range of 100 to 1,000 (in centiseconds).
Description
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
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