Cisco Certified Network Associate (CCNA) Practice Exam

Which Cisco proprietary VPN tunneling protocol relies on the tunneled protocol for encryption?

1. Point-to-Point Tunneling Protocol

2. Layer 2 Tunneling Protocol

3. Layer 2 Forwarding

4. IPsec

The correct answer is: Layer 2 Forwarding

The correct choice aligns with the characteristic of the Layer 2 Tunneling Protocol (L2TP), which is a Cisco proprietary VPN tunneling protocol. L2TP does not provide encryption by itself. Instead, it relies on the underlying data link layer protocol and typically uses protocols such as IPsec for encryption when implemented in conjunction with it. Point-to-Point Tunneling Protocol (PPTP) and L2TP are both tunneling protocols but they differ significantly; PPTP does have built-in encryption capabilities although it's often considered less secure than L2TP when paired with IPsec. Layer 2 Forwarding (L2F) is another tunneling protocol but is generally regarded as more of an extension of L2TP and does not inherently provide encryption either. IPsec, while a widely used protocol for securing IP communications, is not a tunneling protocol but rather a suite of protocols that provide encryption and authentication over IP networks. Thus, the correct answer clarifies that L2TP relies on the encryption of the tunneled protocol, which makes it a suitable option for contexts requiring the tunneling of protocols while depending on another for security, emphasizing its operation within the VPN landscape as part of a broader encryption strategy.