Huawei Quidway S3900 Series Operation Manual page 251

Operation Manual – MSTP
Quidway S3900 Series Ethernet Switches-Release 1510
when the new spanning trees are generated, loops may occur if the new root ports and
designated ports begin to forward packets immediately.
This can be avoided by adopting a state transition mechanism. With this mechanism,
newly selected root ports and designated ports undergo an intermediate state before
they begin to forward packets. That is, it costs these ports a period (specified by the
Forward delay parameter) for them to turn to the forwarding state. The period ensures
that the newly generated configuration BPDUs to propagate across the entire network.
The Hello time parameter is for link testing.
A switch regularly sends hello packets to other switches in the interval specified by the
Hello time parameter to test the links.
The Max age parameter is used to judge whether or not a configuration BPDU is
obsolete. Obsolete configuration BPDUs will be discarded.
I. Configuration procedure
Table 1-11 Configure MSTP time-related parameters
Operation
Enter system view
Configure the Forward
delay parameter
Configure
time parameter
Configure the Max age
parameter
All switches in a switched network adopt the three time-related parameters configured
on the CIST root bridge.
system-view
stp timer forward-delay
centiseconds
the Hello
stp
centiseconds
stp
centiseconds
Huawei Technologies Proprietary
1-17
Command
timer hello
timer max-age
Chapter 1 MSTP Configuration
Description
—
Required
The Forward
parameter defaults to 1,500
centiseconds (15 seconds).
Required
The Hello time parameter
defaults to
centiseconds (2 seconds).
Required
The Max age parameter
defaults to
centiseconds (20 seconds).
delay
200
2,000