Understanding IP Addresses and Subnet Masks

Table of Contents

• Subnetting
• Broadcast Address vs. Default Gateway vs. Network Address
• Alternative Notation
• Dynamic Host Configuration Protocol (DHCP)
• Your Router’s IP Address is not static after all

For most home users, trying to understand a home network is not of interest due to the perceived complexity of the issue. In this post, whether you are a seasoned engineer or simply a Dad trying to figure out why the router isn’t working again, I will explain the basics of how your home network works.

The first thing we need to understand is what an internet service provider actually does. ISPs are confusing in many cases because they offer more than one service, but in the scope of this post, let’s consider an ISP that offers only internet as a service. An ISP is simply a company that owns hardware (wires) and makes that hardware available to customers in the form of internet service. What are these wires we speak of? Many ISPs own a variety of hardware that all are capable of carrying the analog signals we know as the “internet”.

• Coaxial cables (what you have in your house)
• Unshielded twisted pair (UTP) cables (100 Mhz)
• Shielded twisted pair (STP) cables
• Fiber optic cables (fastest type — many are in the ocean)

There are multiple ways that internet can reach your home, but the most common is through telephone wires (UTP cables). Other methods include underground cables and dish satellites. The method of telephone wires often confuses people because given the name, you would assume that only telephone signals can be sent through telephone wires. This is not the case. The internet bootstrapped off of the phone system, and nowadays, there are multiple channels of communication running through each telephone wire. We call this “broadband” and it is the reason we can talk on the phone, watch Netflix, and search the web all at the same time. Previously, you had to use “dial up” where you would literally “call in” through the phone line to access the internet.