CompTIA Network+

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 can be considered a Layer 2 protocol because it has a pseuodwire mechanism and it can use Layer 2 protocols such as ATM, Frame Relay, and Ethernet. MPLS can also be considered a Layer 3 protocol because it routes data, which is the essence of Layer 3.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 encapsulates existing protocols such as ATM (Asynchronous Transfer Mode), Frame Relay, IP, and many more. MPLS does not use any information in the encapsulated data for routing purposes, and is actually independent of the protocol it is routing.