CCNA Practice Exam 2026 – Complete Study Resource

The Layer 2 Tunneling Protocol (L2TP) primarily uses User Datagram Protocol (UDP) for sending data. It is common to encapsulate L2TP packets within UDP datagrams because this allows for the connection-oriented features of the protocol while providing the benefits of fast transport. Specifically, L2TP typically operates over UDP port 1701, which facilitates the establishment of sessions and allows for tunneling of Layer 2 traffic over IP networks.

Additionally, while L2TP itself does not inherently provide encryption or data integrity services, it is frequently paired with Internet Protocol Security (IPsec) to secure the data being transmitted. This combination helps to ensure both the privacy and authenticity of the data as it traverses less secure networks, but note that IPsec is not directly used by L2TP for data transmission.

Therefore, using UDP is essential for L2TP's functionality, making it a crucial component of the protocol's operation for tunneling.