The primary purpose of protocols at layer 3 of the OSI model is to allow for communication between networks. As you just saw, MAC addresses are used for communication on a single network at layer 2. In much the same fashion, layer 3 is responsible for addresses for internetwork communication. A few protocols can do this, but the most common is the Internet Protocol (IP). Here, we’ll examine IP version 4 (IPv4), which is defined in RFC 791.
In order to understand the functionality of IPv4, you need to know how traffic flows between networks. IPv4 is the workhorse of the communication process and is ultimately responsible for carrying data between devices, regardless of where the communication endpoints are located.
A simple network ...