Advanced Networking Administrator Test Prep

Answer: D - MPLS operates at an OSI Model layer that lies between Layer 2 (Data Link Layer) and Layer 3 (Network Layer). It is often referred to as a "Layer 2.5" protocol.

Key Takeaway: MPLS is not a Layer 2 protocol because the Layer 2 encapsulation is still present with labeled packets. MPLS is not a Layer 3 protocol because the Layer 3 protocol is still present. It is a core networking technology that operates between Layers 2 and 3 of the OSI model. For this reason, MPLS has been referred to as operating at Layer 2.5. MPLS can overlay existing technologies such as ATM (Asynchronous Transfer Mode) or Frame Relay, or it can operate in an entirely IP native environment.