Cisco Certified Network Professional 2025 – 400 Free Practice Questions to Pass the Exam

The protocol that is used to encrypt GRE (Generic Routing Encapsulation) packets is IPSec. GRE itself does not provide encryption or confidentiality; it is designed to encapsulate a wide variety of protocols over a point-to-point link. Because of this limitation, IPSec is often used in conjunction with GRE to provide the necessary encryption and security features.

IPSec is specifically designed to secure Internet Protocol (IP) communications by authenticating and encrypting each IP packet in a communication session. When used with GRE, IPSec can protect the data that is being transported, thus ensuring that sensitive information remains confidential while it flows over the network.

The other options, while related to security in different contexts, do not specifically address the need for encrypting GRE packets. SSL and HTTPS are more relevant to securing web traffic and establishing secure connections over the Internet. SSH is primarily used for secure shell access to network devices and servers, providing command-line access with encryption but not used for encapsulating and securing protocols like GRE. Therefore, IPSec is the suitable choice for encrypting GRE packets, making it the correct answer.