Which statement best describes GRE?

Which statement best describes GRE?

• A. It is a data link layer protocol
• B. It is a routing protocol
• C. It is a transport protocol
• D. It is a tunneling protocol used to encapsulate IP packets inside IP tunnels

Answer: (D)

GRE is a tunneling protocol that creates virtual point-to-point links by encapsulating an IP packet inside another IP packet. This lets different network-layer traffic be carried over an IP network as if it were a simple link between two routers, which is why you can transport IP packets (and even other protocols) inside an IP tunnel. It operates at the network layer and does not function as a data link protocol, a routing protocol, or a transport protocol, which is why the tunneling-description best fits. In practice, GRE tunnels are often used to connect distant networks and can be paired with encryption like IPsec for security.

GRE is a tunneling protocol that creates virtual point-to-point links by encapsulating an IP packet inside another IP packet. This lets different network-layer traffic be carried over an IP network as if it were a simple link between two routers, which is why you can transport IP packets (and even other protocols) inside an IP tunnel. It operates at the network layer and does not function as a data link protocol, a routing protocol, or a transport protocol, which is why the tunneling-description best fits. In practice, GRE tunnels are often used to connect distant networks and can be paired with encryption like IPsec for security.