Cisco Certified Network Associate (CCNA) Practice Exam

Which of the following is NOT a mode of IPsec?

1. Transport mode

2. Tunnel mode

3. Secure mode

4. End-to-end mode

The correct answer is: Secure mode

IPsec (Internet Protocol Security) is a comprehensive suite of protocols aimed at securing Internet Protocol (IP) communications through authentication and encryption of each IP packet in a communication session. The two primary modes of IPsec are Transport mode and Tunnel mode. Transport mode is utilized for end-to-end communication between two hosts. In this mode, only the payload of the IP packet is encrypted and/or authenticated, leaving the original IP header intact. This is optimal for scenarios where security is needed between two communicating hosts without altering routing information. Tunnel mode, on the other hand, is designed for network-to-network communications and is commonly used in Virtual Private Networks (VPNs). In this mode, the entire original IP packet is encapsulated within a new IP packet, which has a new IP header. This allows for secure communication across untrusted networks while effectively masking the original IP addresses. The term "Secure mode" does not correspond to any established mode within IPsec, therefore, it is identified as the option that is NOT a mode of IPsec. Similarly, "End-to-end mode," while it might describe a model of communication, does not specifically describe a mode within the IPsec framework. Recognizing the common modes of IPsec helps in understanding how secure communication