Which protocol is typically used for centralized AAA in mixed vendor environments and uses UDP?

• A. RADIUS
• B. TACACS+
• C. In-Band Authentication
• D. MFA

Answer: (A)

Centralized AAA in mixed vendor environments relies on a protocol designed for shared policy and accounting data across many devices. RADIUS fits this role by providing authentication, authorization, and accounting between a network access server and a central AAA server. It operates over UDP, making it efficient for high-volume authentication requests from diverse equipment such as routers, switches, VPN gateways, and wireless access points. The protocol uses a shared secret to protect the password in transit and delivers accounting information to the server for auditing. TACACS+ can also do AAA but runs over TCP and is often favored for device administration, which makes it less universal for general network access across different vendors. In-band authentication and MFA are not the network AAA protocol in this scenario, with MFA being a method rather than a transport protocol.