Cisco Certified Network Associate (CCNA) Practice Exam

What is the primary purpose of Transport mode in IPsec?

1. Encrypting the entire packet

2. Providing a secure tunnel for site-to-site connections

3. Encrypting only the payload of the packet

4. Securing web browser connections

The correct answer is: Encrypting only the payload of the packet

The primary purpose of Transport mode in IPsec is to encrypt only the payload of the packet, which includes the actual data being transported, while leaving the original header intact. This is significant because it allows the end devices to communicate securely without needing to encapsulate the entire packet within a new header, as is done in Tunnel mode. By only encrypting the payload, Transport mode is suitable for end-to-end communications between two hosts, such as in client-server scenarios where both endpoints need access to the original IP addressing information for routing and delivery. Transport mode is often used when the security needs are focused on the data itself rather than on securing the communication pathway, making it an efficient choice for scenarios where the identities of the endpoints are already trusted. This contrasts with Tunnel mode, which is typically used for secure site-to-site connections, where it encapsulates the entire original packet to provide complete anonymity and protection between two networks over the internet.