Configuring The Maximum Hop Count Of An Mst Region - H3C S5100-SI Operation Manual

To do...
Enter system view
Configure the MSTP operation
mode
Configuration example
# Specify the MSTP operation mode as STP-compatible.
<Sysname> system-view
[Sysname] stp mode stp

Configuring the Maximum Hop Count of an MST Region

The maximum hop count configured on the region root is also the maximum hops of the MST region.
The value of the maximum hop count limits the size of the MST region.
A configuration BPDU contains a field that maintains the remaining hops of the configuration BPDU.
And a switch discards the configuration BPDUs whose remaining hops are 0. After a configuration
BPDU reaches a root bridge of a spanning tree in an MST region, the value of the remaining hops field
in the configuration BPDU is decreased by 1 every time the configuration BPDU passes one switch.
Such a mechanism disables the switches that are beyond the maximum hop count from participating in
spanning tree calculation, and thus limits the size of an MST region.
With such a mechanism, the maximum hop count configured on the switch operating as the root bridge
of the CIST or an MSTI in an MST region becomes the network diameter of the spanning tree, which
limits the size of the spanning tree in the current MST region. The switches that are not root bridges in
the MST region adopt the maximum hop settings of their root bridges.
Configuration procedure
Follow these steps to configure the maximum hop count for an MST region:
To do...
Enter system view
Configure the maximum hop
count of the MST region
The bigger the maximum hop count, the larger the MST region is. Note that only the maximum hop
settings on the switch operating as a region root can limit the size of the MST region.
Configuration example
# Configure the maximum hop count of the MST region to be 30.
<Sysname> system-view
[Sysname] stp max-hops 30
Use the command...
system-view
stp mode { stp | rstp | mstp }
Use the command...
system-view
stp max-hops hops
1-22
Remarks
—
Required
An MSTP-enabled switch
operates in the MSTP mode by
default.
Remarks
—
Required
By default, the maximum hop
count of an MST region is 20.