Which of the following is mainly used for remote access into the network?

A.
XTACACS

B.
TACACS+

C.
Kerberos

D.
RADIUS

Explanation:
Most gateways that control access to the network have a RADIUS client component that communicates with the RADIUS server. Therefore, it can be inferred that
RADIUS is primarily used for remote access.
Incorrect Answers:
A: XTACACS has been replaced by RADIUS and TACACS+.
B: The separate components of the TACACS+ protocol is segregated and handled on different servers, whereas the RADIUS protocol is centralized. This means
that not only TACACS+ is used by the TACACS+ protocol for remote access.
C: Kerberos is primarily used for the protection for logon credentials.

http://en.wikipedia.org/wiki/RADIUS
http://en.wikipedia.org/wiki/TACACS
http://en.wikipedia.org/wiki/Kerberos_(protocol)