Introduction to the Internet


Hosts are computers at the beginning or end of network traffic:

Client and Server

What are IP addresses?

Client to server communication with source an destination IP addresses shown

Requests and responses are put into IP packets. The IP packet contains the source and destination IP addresses. After that comes the payload of the packet: A request or response in our case.

IP addresses are hierarchical

The example company has the IP address space starting with 10. The company can assign one of its branches a subnet, for example 10.20.x.x.

This subnet can again be divided up into different subnets like 10.20.55.x, forming a hierarchy.

A host in that subnet is for example The hierarchy of the network allows us to find this host using its IP address.


Create a single network with a switch

How switches work.

Connect networks with a router

Routers connect the hierarchy of networks

Summary: Switches, routers, and hosts

Hosts with switches and router in between

Combined device: Residential gateway

Residential gateway Residential gateway explanation
A residential gateway is commonly called just a "router" but it's also a switch, wireless access point (for Wi-Fi), and often provides a local web server for configuring the network.

The Internet

Home network → Internet

A (somewhat hierarchical) network of networks