H3C Technologies H3C S12500 Series Switches - Manual (Page 90)

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long, it might take a long time for the network to converge. H3C recommends you to use the default
setting.
• An appropriate hello time setting enables the switch to promptly detect link failures on the network
without using excessive network resources. If the hello time is too long, the switch will consider
packet loss as a link failure and trigger a new spanning tree calculation process. If the hello time is
too short, the switch will frequently send the same configuration BPDUs, which add the device
burden and waste network resources. H3C recommends you to use the default setting.
• If the max age timer is too short, the switch will frequently launch spanning tree calculation and
might consider network congestion as a link failure. If the max age timer is too long, the switch
might fail to detect link failures and launch spanning tree calculations promptly, reducing the
auto-sensing capability of the network. H3C recommends you to use the default setting.
Configuration procedure
To configure the spanning tree timers:
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure the forward delay
timer.
• In STP/RSTP/MSTP mode:
stp timer forward-delay time
• In PVST mode:
stp vlan vlan-list timer
forward-delay time
Optional.
Use either command.
The default setting is 1500
centiseconds.
3. Configure the hello timer.
• In STP/RSTP/MSTP mode:
stp timer hello time
• In PVST mode:
stp vlan vlan-list timer hello time
Optional.
Use either command.
The default setting is 200
centiseconds.
4. Configure the max age timer.
• In STP/RSTP/MSTP mode:
stp timer max-age time
• In PVST mode:
stp vlan vlan-list timer max-age
time
Optional.
Use either command.
The default setting is 2000
centiseconds.
Configuring the timeout factor
The timeout factor is a parameter used to decide the timeout time, in the following formula: Timeout time
= timeout factor × 3 × hello time.
After the network topology is stabilized, each non-root-bridge device forwards configuration BPDUs to
the downstream devices at the interval of hello time to check whether any link is faulty. If a device does
not receive a BPDU from the upstream device within nine times the hello time, it assumes that the
upstream device has failed and starts a new spanning tree calculation process.
Sometimes a device might fail to receive a BPDU from the upstream device because the upstream device
is busy. If a spanning tree calculation occurs, the calculation can fail and also waste the network
resources. In a stable network, you can prevent undesired spanning tree calculations by setting the
timeout factor to 5, 6, or 7.
To configure the timeout factor: