Configuring The Timeout Factor - H3C SR8800 Configuration Manual

2 × (forward delay – 1 second) ƒ max age
•
• Max age ƒ 2 × (hello time + 1 second)
H3C does not recommend you to manually set the spanning tree timers. Instead, you can specify the
network diameter and let spanning tree protocols automatically calculate the timers based on the
network diameter. If the network diameter uses the default value, the timers also use their default values.
Configure the timers on the root bridge only, and the timer settings on the root bridge apply to all the
routers on the entire switched network.
To configure the spanning tree timers:
Step
1. Enter system view.
2. Configure the forward delay
timer.
3. Configure the hello timer.
4. Configure the max age timer.
NOTE:
The length of the forward delay timer is related to the network diameter of the switched network. The
•
larger the network diameter is, the longer the forward delay time should be. If the forward delay timer
is too short, temporary redundant paths may be introduced. If the forward delay timer is too long, it may
take a long time for the network to converge. H3C recommends you to use the default setting.
An appropriate hello time setting enables the router to timely detect link failures on the network without
•
using excessive network resources. If the hello time is too long, the router will consider packet loss as a
link failure and trigger a new spanning tree calculation process. If the hello time is too short, the router
will frequently send the same configuration BPDUs, which add the router burden and waste network
resources. H3C recommends you to use the default setting.
If the max age timer is too short, the router will frequently launch spanning tree calculation and may
•
consider network congestion as a link failure. If the max age timer is too long, the router may fail to
timely detect link failures and launch spanning tree calculation, reducing the auto-sensing capability of
the network. H3C recommends you to use the default setting.

Configuring the timeout factor

The timeout factor is a parameter used to decide the timeout time, as shown in the following formula:
Timeout time = timeout factor × 3 × hello time.
After the network topology is stabilized, each non-root-bridge router forwards configuration BPDUs to the
downstream routers at the interval of hello time to check whether any link is faulty. If a router does not
receive a BPDU from the upstream router within nine times the hello time, it assumes that the upstream
router has failed and starts a new spanning tree calculation process.
Command
system-view
stp timer forward-delay time
stp timer hello time
stp timer max-age time
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Remarks
N/A
Optional.
The default setting is 1500
centiseconds.
Optional.
The default setting is 200
centiseconds.
Optional.
The default setting is 2000
centiseconds.