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Which two statements are correct? (Choose two.)

Refer to the Exhibit.

As shown in the exhibit, Switch-3 receives a superior BPDU from Switch-2 over the ge-0/0/10.0 interface.

Which two statements are correct? (Choose two.)

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A.
Switch-2’s ge-0/0/10.0 port assumes the backup role and blocking state.

B.
Switch-3’s ge-0/0/10.0 port assumes the designated role and forwarding state.

C.
Switch-2’s ge-0/0/10.0 port assumes the designated role and forwarding state.

D.
Switch-3’s ge-0/0/10.0 port assumes the alternate role and blocking state.

Explanation:
Root Guard is useful in avoiding Layer 2 loops during network anomalies. The Root Guard feature forces an interface to become a designated port to prevent surrounding switches from becoming a root switch. In other words, Root Guard provides a way to enforce the root bridge placement in the network. The Root Guard feature prevents a Designated Port from becoming a Root Port. If a port on which the Root Guard feature receives a superior BPDU, it moves the port into a root-inconsistent state (effectively equal to a listening state), thus maintaining the current Root Bridge status.

The Root Guard feature prevents a port from becoming a Root Port, thus ensuring that the port is always a Designated Port. Unlike other STP enhancements, which can also be enabled on a global basis, Root Guard must be manually enabled on all ports where the Root Bridge should not appear. Because of this, it is important to ensure a deterministic topology when designing and implementing STP in the LAN. After the Root Guard feature is enabled on a port, the switch does not enable that port to become an STP root port. The port remains as an STP designatedport. In addition, if a better BPDU is received on the port, Root Guard disables (err-disables)the port rather than processing the BPDU. If an unauthorized device starts sending BPDUs with a better bridge ID, the normal STP process would elect the new switch as the root switch. By disabling the port, the network topology is protected.


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