3Com Switch 8800 Configuration Guide
Chapter 38 MSTP Region-configuration
38-17
Restore the default MSTP running mode
undo stp
mode
Generally, if there is a STP switch on the switching network, the port connected to it will
automatically transit from MSTP mode to STP-compatible mode. But the port cannot
automatically transit back to MSTP mode after the STP switch is removed. In this case,
you can execute the
stp mcheck
command to restore the MSTP mode.
By default, MSTP runs in MSTP mode.
38.2.4 Configuring the Bridge Priority for a Switch
Whether a switch can be elected as the spanning tree root depends on its Bridge
priority. The switch configured with a smaller Bridge priority is more likely to become the
root. An MSTP switch may have different priorities in different STIs.
You can use the following command to configure the Bridge priorities of the Designated
bridge in different STIs.
Perform the following configuration in system view.
Table 38-6
Configure the Bridge priority for a switch
Operation
Command
Configure the Bridge priority of the
Designated bridge
stp
[
instance
instance
-
id
]
priority
priority
Restore the default Bridge priority of the
Designated bridge
undo stp
[
instance
instance
-
id
]
priority
When configuring the switch priority with the
instance
instance
-
id
parameter as 0, you
are configuring the CIST priority of the switch.
Caution:
In the process of spanning tree root election, of two or more switches with the same
Bridge priorities, the one has a smaller MAC address is elected as the root.
By default, the switch Bridge priority is 32768.
38.2.5 Configuring the Max Hops in an MST Region
The scale of MST region is limited by the max hops in an MST region, which is
configured on the region root. As the BPDU travels from the spanning tree root, each
time when it is forwarded by a switch, the max hops is reduced by 1. The switch
