3Com MSR 30, MSR 50 manual Stp timer max-age

626CHAPTER 38: MSTP CONFIGURATION COMMANDS

interval of the hello time set on the device, while secondary root bridges use the hello time set on the root bridge.

The setting of the hello time, forward delay and max age timers must meet the following formulae.

■2 ⋅ (forward delay - 1 second) ƒ max age

■Max age ƒ 2 ⋅ (hello time + 1 second)

MSTP can work effectively on the entire network only when the above-mentioned conditions are met; otherwise, network instability will frequently occur. We recommend that you specify the network diameter of the switched network in the stp bridge-diameterbridge-numbercommand and let MSTP automatically calculate an optimal setting of these three timers.

Related commands: stp timer forward-delay,stp timer max-age, and stp bridge-diameter.

Examples # Set the hello time of the device to 400 centiseconds.

<Sysname> system-view

[Sysname] stp timer hello 400

stp timer max-age

Syntax stp timer max-age centi-seconds

undo stp timer max-age

View System view

Parameters centi-seconds: Max age, in the range 600 to 4,000 (in centiseconds). This argument must be a multiple of 100.

Description Use the stp timer max-agecommand to set the max age timer of the device.

Use the undo stp timer max-agecommand to restore the max age timer of the device to the default setting.

By default, the max age is set to 2,000 centiseconds.

MSTP can detect link faults and automatically restore the forwarding state of the redundant link. In the CIST, the device determines whether a configuration BPDU received on a port has expired based on the max age timer. If a port receives a configuration BPDU that has expired, that MST instance needs to re-computed.

The max age timer is not meaningful for MSTIs. If the current device is the root bridge of the CIST, it determines whether a configuration BPDUs has expired based on the configured max age timer; if the current device is not the root bridge of the CIST, it uses the max age timer set on the CIST root bridge.