Cisco Certified Network Associate (CCNA) Practice Exam

What is the primary use case for Transport Mode in IPsec?

1. Network-to-Network Communications

2. Host-to-Host Communications

3. Site-to-Site Communications

4. VPN Gateway Communication

The correct answer is: Host-to-Host Communications

Transport Mode in IPsec is primarily designed for end-to-end communications between hosts. This mode focuses on the communication established between two devices, encrypting only the payload of the IP packets and leaving the header intact, which allows for efficient routing. This is particularly useful when secure communication is needed between two specific systems, without the need for the entire network traffic to be encapsulated, as would happen in Tunnel Mode. By using Transport Mode for host-to-host communications, data integrity, authentication, and confidentiality can be maintained while allowing for flexibility, as the original IP addressing remains in the packet headers. This mode is typically used in scenarios where both communicating hosts are aware of and can directly process the IPsec processing, such as in secure communications between individual devices like servers or endpoints. This mode is not generally suited for network-to-network or site-to-site connections, where Tunnel Mode would be more appropriate due to its ability to encapsulate entire packets and address the needs of multiple networks communicating securely.