Huawei Quidway S6500 Series Operation Manual page 409

Operation Manual - STP
Quidway S6500 Series Ethernet Switches
Table 1-10 Configure the time parameters of a switch
Configure Forward Delay on the switch.
Restore the default Forward Delay of the
switch.
Configure Hello Time on the switch.
Restore the default Hello Time on the switch.
Configure Max Age on the switch.
Restore the default Max Age on the switch.
Every switch on the switching network adopts the values of the time parameters
configured on the root bridge of the CIST.
Caution:
The Forward Delay configured on a switch depends on the switching network
diameter. Generally, the Forward Delay is supposed to be longer when the network
diameter is longer. Note that too short a Forward Delay may redistribute some
redundant routes temporarily, while too long a Forward Delay may prolong the
network connection resuming. The default value is recommended.
A suitable Hello Time ensures the switch to detect the link fault on the network but
occupy moderate network resources. The default value is recommended. If you set
too long a Hello Time, when there is packet dropped over a link, the switch may
consider it as link fault and the network device will recalculate the spanning tree
accordingly. However, for too short a Hello Time, the switch frequently sends
configuration BPDU, which adds its burden and wastes the network resources.
Too short a Max Age may cause the network device frequently calculate the
spanning tree and mistake the congestion as link fault. However, if the Max Age is
too long, the network device may not be able to discover the link fault and
recalculate the spanning tree in time, which will weaken the auto-adaptation
capacity of the network. The default value is recommended.
To avoid frequent network flapping, the values of Hello Time, Forward Delay and
Maximum Age should guarantee the following formulas equal.
2 * (forward-delay - 1seconds) >= maximum-age
maximum-age >= 2 * (hello + 1.0 seconds)
Operation
Huawei Technologies Proprietary
1-17
Chapter 1 MSTP Region-configuration
Command
stp timer forward-delay
centiseconds
undo stp timer forward-delay
stp timer hello centiseconds
undo stp timer hello
stp timer max-age centiseconds
undo stp timer max-age