3Com Switch 8800 Family Configuration Guide

Configuring MSTP 137
each time when it is forwarded by a switch, the max hops is reduced by 1. The
switch discards the configuration BPDU with 0 hops left. This makes it impossible
for the switch beyond the max hops to take part in the spanning tree calculation,
thereby limiting the scale of the MST region.
You can use the following command to configure the max hops in an MST region.
Perform the following configuration in system view.
The more the hops in an MST region, the larger the scale of the region. Only the
max hops configured on the region root can limit the scale of MST region. Other
switches in the MST region also apply the configurations on the region root, even
if they have been configured with max hops.
By default, the max hop of an MST is 20.
Configuring the
Switching Network
Diameter
Any two hosts on the switching network are connected with a specific path
carried by a series of switches. Among these paths, the one passing more switches
than all others is the network diameter, expressed as the number of passed
switches.
You can use the following command to configure the diameter of the switching
network.
Perform the following configuration in system view.
The network diameter is the parameter specifying the network scale. The larger
the diameter is, the lager the scale of the network is.
When a user configures the network diameter on a switch, MSTP automatically
calculates and sets the Hello Time, Forward-Delay and Max Age time of the switch
to the desirable values.
Setting the network diameter takes effect on CIST only, but has no effect on MSTI.
By default, the network diameter is 7 and the three corresponding timers take the
default values.
n
The stp bridge-diameter command configures the switching network diameter
and determines the three MSTP time parameters (Hello Time, Forward Delay, and
Max Age) accordingly.
Tab le 111 Configure the max hops in an MST region
Operation Command
Configure the max hops in an MST region stp max-hops hop
Restore the default max hops in an MST region undo stp max-hops
Tab le 112 Configure the switching network diameter
Operation Command
Configure the switching network diameter stp bridge-diameter bridgenum
Restore the default switching network diameter undo stp bridge-diameter