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194 CHAPTER 8: STP OPERATION
Configuring the Max
Hops in an MST Region
The scale of an MST region is limited by the max hops in the MST region; which is
configured on the region root. As the BPDU travels from the spanning tree root,
each time it is forwarded by a switch, the max hop 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 hops 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, the larger the scale.
When a user configures the network diameter on a switch, MSTP automatically
calculates and sets the hello time, forward-delay time, and maximum-age time, of
the switch, to the desirable values.
The setting of 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.
Table 195 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
Table 196 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