User's Manual

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mode. Switches running in MSTP-compatible mode can identify the message structure of other MSTPs, check
the contained MST regional identifier and establish the MST region.
The MST-compatible mode and the STP-compatible mode are based on MSTPprotocol conversion mechanism.
If one port of the switch receives BPDU in compatible mode, the port automatically changes to the mode and
sends BPDU in compatible mode. To resume the port to standard MST mode, you can run spanning-tree
mstpmigration-check.
In global configuration mode, run the following commands to enable or disable theMST-compatible mode:
Command Purpose
spanning-tree mstp mst-compatible
Enable the MST-compatible mode of the switch.
no spanning-tree mstp mst-compatible
Disable the MST-compatible mode of the switch.
Note:
The main function of the compatible mode is to create the MST area for switches and other MSTP-runningswitches. In
actual networking, make sure that the switch has the same configuration name and the same edit number. It is
recommended to configure switches running other MSTP protocols to the CIST root, ensuring that the switch enters the
compatible mode by receiving message.
If the MST-compatible mode is not activated, the switch will not resolve the whole BPDU-compatiblecontent and take
the content as the common RSTP BPDU. In this way, the switch cannot be in the samearea with the MST-compatible
switch that it connects.
A port in compatible mode cannot automatically resumes to send standard MST BPDU even if
thecompatible mode is shut down in global configuration mode. In this case, run migration-check.
36.3.15 Restarting the protocol conversion check
MSTP allows the switch to work with the traditional STP switch through protocolconversion mechanism. If one
port of the switch receives the STP configuration message, the port then only transmits the STP message. At
the same time, the port that receives the STP information is then considered as a boundary port. Likewise, in
MST compatible mode, if one interface receives the compatible BPDU, the interface will also forward
compatible BPDU.
Note:
When a port is in the STP-compatible state, the port will not automatically resume to the MSTP
state even if the port does not receive the STP message any more. In this case, you can run
spanning-tree mstpmigration-check to clear the STP message that the port learned, and make
the port to return to the MSTPstate.
The switch that runs the RSTP protocol can identify and handle the MSTP message. Therefore, the MSTP
switch does not require protocol conversion when it works with the RSTP switch.
In global configuration mode, run the following command to clear all STP informationthat is detected by all
ports of the switch:
Command Purpose
spanning-tree mstp migration-check
Clears all STP information that is detected by all
ports of the switch.
In port configuration mode, run the following command to clear STP informationdetected by the port.