How do you enable Root Guard on a specific interface in RSTP?

Enabling Root Guard on a specific interface in Rapid Spanning Tree Protocol (RSTP) involves configuring the specific interface to enforce the root guard feature. This can be achieved by entering the interface configuration mode and applying the command spanning-tree guard root. This command allows the designated port to protect the root bridge by preventing any other switch from becoming the root bridge on that segment. If a superior Bridge Protocol Data Unit (BPDU) is received on a port where Root Guard is enabled, that port will be put into a root-inconsistent state and will not transition into forwarding until the condition is resolved.

The other methods described do not specifically apply Root Guard to an individual interface. Enabling Root Guard globally would not give you the granularity to apply the feature selectively, and using the command spanning-tree feature root is not a recognized method for enabling Root Guard. Lastly, stating that Root Guard is automatically enabled on all ports is incorrect; it must be configured explicitly on the desired interfaces.