Which of the following should be allowed through a firewall to easy communication and usage by users?

A.
RIP

B.
IGRP

C.
DNS

D.
OSPF

Explanation:
DNS translates domain names into IP addresses, which enables us to use domain names instead of IP
addresses.
Incorrect Answers:
A: RIP is a routing protocol. A routing protocol forwards routing information between routers, but does make it
easier for users to communicate.
B: IGRP is a routing protocol. A routing protocol forwards routing information between routers, but does make it
easier for users to communicate.
D: OSPF is a routing protocol. A routing protocol forwards routing information between routers, but does make
it easier for users to communicate.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 599