How does an AR router determine a same MST region


The device fails to learn correct MAC entries because:
- The device does not receive packets because a link is Down, an interface is not added to a VLAN, an interface joins in loop protocol calculation and is blocked, or the MAC address drift detection is configured and an interface or a MAC address is blocked.
- There is a loop in the network, causing MAC entry flapping.
- The MAC address learning function is disabled, or corresponding sticky MAC address already exists.
- The number of MAC entries has reached the upper limit of the device.
- A static or blackhole route is configured.

Other related questions:
Method of querying card models on an AR router
Run the display device command or the display elabel command on an AR router to query component types of the router. The card names obtained using these two commands may be different, because the card names obtained by running the display device command are planned in advance but electronic labels are unique IDs of the cards and will not change with software upgrades.

How do I determine whether devices belong to the same MST region
Check whether the region configurations on devices are the same. If so, the devices belong to the same Multiple Spanning Tree (MST) region. If not, the devices belong to different MSTP regions. For example, devices with the same region name, VLAN-instance mapping, and revision level belong to the same region.

Is the MSTP status of interfaces affected when the MSTP status of a member interface in the MST region changes
Yes. When the MSTP status of a member interface in the MST region changes, the device recalculates the MSTP status of all member interfaces in the MST region.

Does a change in the MSTP status of an AR router interface affect the MSTP status of other interfaces in the same MST region
If the MSTP status of an interface changes, the device will recalculate the status of all other interfaces in the MST region.

Why is the convergence for multiple MST regions slow
When a specified interface of the root bridge is faulty, the two packets that contain different root bridge information in an MST region may interact with each other continuously. The root bridge selection flaps for a period. As a result, the negotiation time is long and the network convergence is slow. Using the stp max-hops command, you can properly limit the maximum number of hops as required. Thus, the root bridge can be quickly confirmed and the convergence time can be shortened.

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