3Com 8807 Configuration Manual page 136

136 C 17: MSTP R
HAPTER
Configuring the Bridge
Priority for a Switch
c
Configuring the Max
Hops in an MST Region
-
EGION CONFIGURATION
the switch ports send MSTP or STP packets (when connected to the STP switch)
and the switch provides multiple spanning tree function.
You can use the following command to configure MSTP running mode. MSTP can
intercommunicate with STP. If there is a STP switch in the switching network, you
may use the command to configure the current MSTP to run in STP-compatible
mode. Otherwise, configure it to run in MSTP mode.
Perform the following configuration in system view.
Table 109 Configure the MSTP running mode
Operation
Configure MSTP to run in STP-compatible mode
Configure MSTP to run in MSTP mode
Restore the default MSTP running 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, the switch runs in MSTP mode.
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 110 Configure the Bridge priority for a switch
Operation
Configure the Bridge priority of the
Designated bridge
Restore the default Bridge priority of the
Designated bridge
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.
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,
Command
stp mode stp
stp mode mstp
undo stp mode
Command
stp [ instance instance-id ] priority priority
undo stp [ instance instance-id ] priority