F3726, F3211, F3174, R5135, R3816-HP Firewalls and UTM Devices Network Management Configuration Guide-6PW100

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HP does not recommend manually setting the spanning tree timers. Instead, HP recommends specifying
the network diameter and using the automatically calculated timers based on the network diameter. If the
network diameter uses the default value, the timers also use their default values.
Configure timers on the root bridge only. Timer settings on the root bridge apply to all devices on the
entire switched network.
1139BConfiguration guidelines
• 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 might occur. If the forward delay timer is too long,
network convergence might take a long time. HP recommends you to use the default setting.
• An appropriate hello time setting enables the device to promptly detect link failures on the network
without using excessive network resources. If the hello time is too long, the device will mistake
packet loss as a link failure and trigger a new spanning tree calculation process. If the hello time is
too short, the device will frequently send the same configuration BPDUs, which add the device
burden and waste network resources. HP recommends you to use the default setting.
• If the max age timer is too short, the device will frequently launch spanning tree calculation and
may mistake network congestion as a link failure. If the max age timer is too long, the device may
fail to detect link failures and launch spanning tree calculations promptly, reducing the auto-sensing
capability of the network. HP recommends you to use the default setting.
1140BConfiguration procedure
To configure the spanning tree timers:
Ste
p
Command Remarks
138. Enter system view. system-view N/A
139. Configure the forward
delay timer.
stp timer forward-delay time
Optional.
Use one of the commands.
The default setting is 15 seconds.
140. Configure the hello timer.
stp timer hello time
Optional.
Use one of the commands.
The default setting is 2 seconds.
141. Configure the max age
timer.
stp timer max-age time
Optional.
Use one of the commands.
The default setting is 20 seconds.
433BConfiguring the timeout factor
The timeout factor is a parameter used to calculate the timeout time in the following formula: Timeout time
= timeout factor × 3 × hello time.
After the network topology stabilizes, each non-root-bridge device forwards configuration BPDUs to
downstream devices at the interval of hello time to determine whether any link is faulty. If a device does
not receive a BPDU from the upstream device within nine times (the default timeout factor x 3) 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. In this case, if a spanning tree calculation occurs, the calculation can fail and also waste network