3com S7906E Guide De Référence
1-34
z
2 × (forward delay – 1 second) ú max age
z
Max age ú 2 × (hello Time + 1 second)
MSTP can work effectively on the entire network only when the above-mentioned conditions are met;
otherwise, topology changes will frequently occur. We recommend that you specify the network
diameter of the switched network in the stp root primary command and let MSTP automatically
calculate optimal settings of these three timers.
Related commands: stp timer hello, stp timer max-age, stp bridge-diameter.
Examples
# Set the forward delay timer of the device to 2,000 centiseconds.
<Sysname> system-view
[Sysname] stp timer forward-delay 2000
stp timer hello
Syntax
stp timer hello centi-seconds
undo stp timer hello
View
System view
Default Level
2: System level
Parameters
centi-seconds: Hello time (in centiseconds), ranging from 100 to 1000 in steps of 100.
Description
Use the stp timer hello command to set the hello time of the device.
Use the undo stp timer hello command to restore the system default.
By default, the hello time is set to 200 centiseconds.
Hello time is the time interval at which MSTP-enabled devices send configuration BPDUs to maintain
spanning tree. If a device fails to receive configuration BPDUs within the set period of time, a new
spanning tree calculation process will be triggered due to timeout. The root bridge sends configuration
BPDUs at the interval of the hello time set on the device, while secondary root bridges use the hello time
set on the root bridge.
The settings of the hello time, forward delay and max age timers must meet the following formulae:
z
2 × (forward delay – 1 second) ú max age
z
Max age ú 2 × (hello time + 1 second)
MSTP can work effectively on the entire network only when the above-mentioned conditions are met;
otherwise, topology changes will frequently occur. We recommend that you specify the network
diameter of the switched network in the stp root primary command and let MSTP automatically
calculate optimal settings of these three timers.
Related commands: stp timer forward-delay, stp timer max-age, stp bridge-diameter.