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Private vs. Public IPv4 Addressing

CCNA: 0 to Hero - Comprehensive Network Engineering Bootcamp

Lesson 14: Private vs. Public IPv4 Addressing

Due to the limited supply of IPv4 addresses, certain ranges are reserved for use within private networks (LANs). These addresses are not routable on the public Internet.

Private IP Address Ranges (RFC 1918)

ClassNetwork RangeCIDR Notation
Class A10.0.0.0 to 10.255.255.25510.0.0.0/8
Class B172.16.0.0 to 172.31.255.255172.16.0.0/12
Class C192.168.0.0 to 192.168.255.255192.168.0.0/16

Public IP Addresses

All addresses outside the RFC 1918 ranges are considered public. These are unique, globally routable addresses assigned to organizations by Internet Registries.

The Role of NAT

Since private addresses cannot traverse the Internet, Network Address Translation (NAT) is used by routers to translate private addresses into one or more public addresses before sending the traffic out to the internet. (We will cover NAT extensively later).