3Com Switch 4800G 24-Port Configuration Manual page 216

216 C 23: MSTP C
HAPTER
Configuring the Work
Mode of MSTP Device
Configuring the Priority
of the Current Device
ONFIGURATION
MSTP will select the secondary root bridge with the lowest MAC address as the
new root bridge.
When specifying the root bridge or a secondary root bridge, you can specify
■
the network diameter and hello time. However, these two options are effective
only for MST instance 0, namely the CIST. If you include these two options in
your command for any other instance, the configuration can succeed, but they
will not actually work. For the description of network diameter and hello time,
refer to "Configuring the Network Diameter of a Switched Network" on page
218 and "Configuring Timers of MSTP" on page 218.
Alternatively, you can also specify the current device as the root bridge by
■
setting the priority of the device to 0. For the device priority configuration,
refer to "Configuring the Priority of the Current Device" on page 216.
Configuration example
# Specify the current device as the root bridge of MST instance 1 and a secondary
root bridge of MST instance 2.
<Sysname> system-view
[Sysname] stp instance 1 root primary
[Sysname] stp instance 2 root secondary
MSTP and RSTP can recognize each other's protocol packets, so they are mutually
compatible. However, STP is unable to recognize MSTP packets. For hybrid
networking with legacy STP devices and full interoperability with RSTP-compliant
devices, MSTP supports three work modes: STP-compatible mode, RSTP mode,
and MSTP mode.
In STP-compatible mode, all ports of the device send out STP BPDUs,
■
In RSTP mode, all ports of the device send out RSTP BPDUs. If the device
■
detects that it is connected with a legacy STP device, the port connecting with
the legacy STP device will automatically migrate to STP-compatible mode.
In MSTP mode, all ports of the device send out MSTP BPDUs. If the device
■
detects that it is connected with a legacy STP device, the port connecting with
the legacy STP device will automatically migrate to STP-compatible mode.
Configuration procedure
Follow these steps to configure the MSTP work mode:
To do...
Enter system view
Configure the work mode of
MSTP
Configuration example
# Configure MSTP to work in STP-compatible mode.
<Sysname> system-view
[Sysname] stp mode stp
The priority of a device determines whether it can be elected as the root bridge of
a spanning tree. A lower value indicates a higher priority. By setting the priority of
Use the command...
system-view
stp mode { stp | rstp | mstp } Optional
Remarks
-
MSTP mode by default