Cisco Certified Network Associate (CCNA) Practice Exam

Which VPN tunneling protocol uses TCP for control packets and GRE for data packets?

1. Layer 2 Forwarding

2. Layer 2 Tunneling Protocol

3. Point-to-Point Tunneling Protocol

4. Tunnel mode

The correct answer is: Point-to-Point Tunneling Protocol

The Point-to-Point Tunneling Protocol (PPTP) is the correct answer because it uses a combination of TCP and GRE to establish a VPN connection. In PPTP, control packets are sent over TCP, which ensures reliable delivery and good error handling for the control information necessary to maintain the connection. On the other hand, the actual data packets are encapsulated and transported using GRE (Generic Routing Encapsulation), which allows for the forwarding of a wide range of Layer 3 protocols across a point-to-point connection. This combination is key for establishing the secure tunnel since TCP is utilized for setting up and managing the tunnel, while GRE is efficient in data forwarding, enabling the transport of packets from the original protocol over the tunnel. The other options involve different protocols that do not use this specific combination of TCP for control and GRE for data. Layer 2 Forwarding and Layer 2 Tunneling Protocol (L2TP), for example, have different architectures and methodologies for encapsulation and do not utilize PPTP's mixture of TCP and GRE in this arrangement. Tunnel mode refers to a method of IPsec VPN where the entire original packet is encapsulated in a new packet, but it does not pertain to a specific tunneling protocol