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Questions and Answers
A RADIUS server sends an Access Reject message if a user's credentials are not valid.
A RADIUS server sends an Access Reject message if a user's credentials are not valid.
True
Access Challenge is a message sent from a RADIUS server to a RADIUS client if the server requires additional information from a user.
Access Challenge is a message sent from a RADIUS server to a RADIUS client if the server requires additional information from a user.
True
Access Accept is sent from a RADIUS server to a client if a user's credentials are invalid.
Access Accept is sent from a RADIUS server to a client if a user's credentials are invalid.
False
TACACS+ is an open-source networking protocol developed by CISCO.
TACACS+ is an open-source networking protocol developed by CISCO.
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TACACS+ combines authentication, authorization, and accounting services into one.
TACACS+ combines authentication, authorization, and accounting services into one.
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RADIUS encrypts the entire content of each AAA packet.
RADIUS encrypts the entire content of each AAA packet.
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TACACS+ can be used to authenticate only users, not devices.
TACACS+ can be used to authenticate only users, not devices.
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TACACS+ uses TCP port 49 for communication.
TACACS+ uses TCP port 49 for communication.
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A TACACS+ server contains authentication information only for users, not devices.
A TACACS+ server contains authentication information only for users, not devices.
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A TACACS+ client can be a Network Access Server (NAS).
A TACACS+ client can be a Network Access Server (NAS).
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Study Notes
Authentication Protocols
- CHAP is an authentication protocol that uses a shared secret to authenticate a client to a server over a point-to-point connection.
- CHAP periodically re-authenticates a client during a communication session.
- CHAP uses a three-way handshake protocol involving a server, client, and shared secret.
CHAP Process
- A server sends a randomly generated challenge string to a client.
- The client combines the server's challenge string with a secret shared with the server.
- The client computes the hash value of the combined string and sends the hash value to the server.
- The server compares the hash value received from the client with the server's own calculated hash value.
Kerberos
- Kerberos is an authentication protocol that uses a ticket-based mechanism to authenticate a user and enable access to a network service.
- Kerberos uses UDP port 88 by default.
- Kerberos is the default authentication protocol in Windows Server 2019.
- A Kerberos realm is a network that uses Kerberos authentication.
- A Kerberos authentication involves three entities: Server, Client, and Key Distribution Center (KDC).
EAP (Extensible Authentication Protocol)
- EAP supports multiple authentication methods, including certificate-based, password-based, and multi-factor authentication.
- EAP defines the format of authentication messages.
- Four EAP message types exist: EAP Request, EAP Response, EAP Success, and EAP Failure.
EAP Authentication Methods
- EAP-TLS (Extensible Authentication Protocol-Transport Layer Security) uses TLS and certificates for mutual authentication.
- EAP-TLS requires both a server and a client certificate.
- EAP-FAST (Extensible Authentication Protocol-Flexible Authentication via Secure Tunneling) uses a Protected Access Credential (PAC) to establish a TLS tunnel.
RADIUS (Remote Authentication Dial-In User Service)
- A RADIUS server validates a user's credentials using an authentication protocol such as CHAP.
- RADIUS server responses: Access Reject, Access Challenge, and Access Accept.
- If a user is successfully authenticated, the RADIUS server grants access to authorized network resources.
TACACS+ (Terminal Access Controller Access-Control System Plus)
- TACACS+ is a proprietary networking protocol developed by CISCO for centralized Authentication, Authorization, and Accounting (AAA) services.
- TACACS+ separates authentication, authorization, and accounting services.
- TACACS+ can be used to authenticate a user or a device.
- TACACS+ uses TCP port 49.
- Unlike RADIUS, TACACS+ encrypts the entire content of each AAA packet.
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Description
Learn about the Challenge Handshake Authentication Protocol (CHAP) which uses a shared secret to authenticate clients to servers over point-to-point connections. Understand how CHAP periodically re-authenticates clients and employs a three-way handshake protocol.
