CCNA Data Center DCICN 640-911 Official Cert Guide

Choose a Classful Network

In the original design for what we know of today as the Internet, companies used registered public classful IP networks when implementing TCP/IP inside the company. By the mid-1990s, an alternative became more popular: private IP networks. This section discusses the background behind these two choices, because it impacts the choice of what IP network a company will then subnet and implement in its enterprise internetwork.

Public IP Networks

The original design of the Internet required that any company that connected to the Internet had to use a registered public IP network. To do so, the company would complete some paperwork, describing the enterprise’s internetwork and the number of hosts existing, plus plans for growth. ...