Company ABC wants to minimize the risk of users plugging unauthorized switches and hubs into...

D (Root Guard): Prevents unauthorized devices from becoming the STP root by blocking superior BPDUs on access ports.

E (BPDU Guard): Immediately shuts down ports that receive unexpected BPDUs, protecting against accidental or malicious connection of switches to access ports.

Why other options are incorrect:

A: Loop Guard protects against unidirectional link failures but not unauthorized devices.

B: PortFast speeds up STP convergence on access ports but does not provide security.

C: DTF (Dynamic Trunking Protocol) is not a security feature.

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