AAA servers usually support the protocol TACACS+ and ____________________ to communicate with enterprise resources.

(A) DHCP
(B) ARP
(C) RADIUS
(D) HTTP

RADIUS is the correct answer.

AAA servers usually support the protocol TACACS+ and RADIUS to communicate with enterprise resources.

Authentication, authorization, and accounting (AAA) manage user activity to and through systems. You can think of AAA in the following manner:

1. Authentication: Who is the user?
2. Authorization: What is the user allowed to do?
3. Accounting: What did the user do?

Cisco implements AAA services in its Identity Services Engine (ISE) platform. AAA servers support the following two protocols to communicate with enterprise resources:

1. TACACS+: TACACS+ A Cisco proprietary protocol that separates each of the AAA functions. Communication is secure and encrypted over TCP port 49. One of the key differentiators of TACACS+ is its ability to separate authentication, authorization, and accounting as separate and independent functions. This is why TACACS+ is so commonly used for device administration, even though RADIUS is still certainly capable of providing device administration AAA.
2. RADIUS: Radius is a network protocol that controls user network access via authentication and accounting. Commonly used by Internet Service Providers (ISPs), cellular network providers, and corporate and educational networks.

The RADIUS protocol serves three primary functions:

1. Authenticates users or devices before allowing them access to a network
2. Authorizes those users or devices for specific network services
3. Accounts for the usage of those services