Cisco Certified Network Associate (CCNA) Practice Exam

At which layer of the OSI model does PPP operate?

1. Layer 1

2. Layer 2

3. Layer 3

4. Layer 4

The correct answer is: Layer 2

PPP, or Point-to-Point Protocol, operates at Layer 2 of the OSI model, which is also known as the Data Link layer. This layer is responsible for establishing, maintaining, and terminating a connection between two directly connected nodes. PPP provides a standard method for transporting multi-protocol datagrams across point-to-point links, allowing for encapsulation of network layer protocols. Having its primary functions at the Data Link layer, PPP facilitates error detection, encapsulation of network layer packets, and support for various network protocols such as IP. It's important to note that this protocol is typically used for both dial-up connections and direct serial links, exemplifying its versatility at this layer. The other layers, such as Layer 1 (Physical), Layer 3 (Network), and Layer 4 (Transport), serve different roles in the OSI model. The Physical layer focuses on the transmission of raw data over a physical medium, the Network layer handles routing and forwarding of packets, and the Transport layer is responsible for end-to-end communication and error recovery. Thus, PPP's role as a Data Link layer protocol underscores its function in link establishment and management.