Cisco Certified Network Associate (CCNA) Practice Exam

What are the two possible authentication methods for PPP?

1. CHAP and EAP

2. RADIUS and TACACS+

3. PAP and CHAP

4. HTTP and HTTPS

The correct answer is: PAP and CHAP

The two possible authentication methods for Point-to-Point Protocol (PPP) are Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). PAP is a simple authentication protocol where the username and password are sent over the link in clear text. It is straightforward to implement but does not provide strong security because the credentials are easily intercepted. In contrast, CHAP is a more secure method as it uses a challenge-response mechanism. Upon establishing a connection, the server sends a challenge to the client, which the client must respond to with a hashed version of the credentials. This means that the actual password is never sent over the link, reducing the risk of interception and providing better protection against replay attacks. The other options listed, such as RADIUS and TACACS+, relate to network authentication protocols but are not direct authentication methods utilized within PPP itself. EAP is an extension of PPP but does not represent a standalone authentication method in the same way as PAP and CHAP. HTTP and HTTPS are protocols used for web communication and are not related to PPP authentication methods. Thus, PAP and CHAP stand out as the two primary authentication methods used specifically for PPP connections.