Stp Timer Max-Age - H3C S7500E Series Command Manual

Command Manual – MSTP
H3C S7500E Series Ethernet Switches

1.1.39 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 centiseconds), in the range of 600 to 4,000.
Description
Use the stp timer max-age command to set the max age timer of the device.
Use the undo stp timer max-age command to restore the system default.
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 spanning tree instance needs to be
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 BPDU 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.
The setting of the hello time, forward delay and max age timers must meet the following
formulae:
2 × (forward delay – 1 second) ú max age
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, network instability will frequently occur. We recommend
that you specify the network diameter in the stp root primary command and let MSTP
automatically calculate an optimal setting of these three timers.
Related commands: stp timer forward-delay, stp timer hello, stp bridge-diameter.
Examples
# Set the max age timer of the device to 1,000 centiseconds.
<Sysname> system-view
[Sysname] stp timer max-age 1000
Chapter 1 MSTP Configuration Commands
1-37