What is the purpose of RFC 1918?

• A. It defines private IP address ranges.
• B. It defines multicast addresses.
• C. It defines the reserved loopback range.
• D. It defines public address allocation.

Answer: (A)

RFC 1918 sets aside three IPv4 address blocks for private networks. These ranges—10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16—are not meant to be routed on the public Internet. That lets organizations use them internally for devices and subnets without needing globally unique public addresses, conserving scarce public address space and enabling technologies like NAT to reach external networks when needed. Routers on the Internet don’t forward traffic to these private ranges, which keeps internal addressing isolated from the global Internet.

The other options refer to different concepts: multicast addresses are used for one-to-many delivery and are defined elsewhere; the loopback range (127.0.0.0/8) is for host-local testing; and public address allocation deals with globally routable addresses assigned for Internet-wide use.