Which of the following best describes private IPv4 addresses?

• A. Globally routable on Internet
• B. Non-routable on public Internet and used inside LANs
• C. Always assigned by RIR
• D. Use in Internet backbone

Answer: (B)

Private IPv4 addresses are reserved for use inside private networks and are not routable on the public Internet. This means routers on the wider Internet will not forward packets that use these addresses, so internal traffic stays within the LAN unless it's translated or tunneled to reach the outside world. This setup helps conserve globally unique IPv4 space and lets organizations design their internal addressing independently of the global Internet. They’re defined in standards (RFC 1918) and include ranges such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. In practice, devices on home or enterprise LANs use these addresses and rely on NAT to access Internet resources. They should not be used in the Internet backbone.