Lately I have been getting a lot of requests to help people with connection problems on their home networks. Because of this, I have decided to write an instructable on how to troubleshoot your home network issues. Before you can troubleshoot your network, it's a good idea to understand how it works. This instructable is designed to teach you how your home network works.

Step 1: What Each of Your Devices Do

In a home network, you will generally have at least one of the following devices:
A modem
A router (wireless or wired)
A network switch

Many times when you have a wireless router supplied by your ISP (internet service provider), it has the modem built in. You can see two routers and a switch in the pictures.

Here is the basics of what each device does:

The modem is the device that sends all of your data to your ISP so that you can communicate on the internet.

The router "routes" between different networks. In the home setup, there will generally be the outside network and your home network (inside network). In addition to routing traffic between two networks, your router will generally have NAT (network address translation) and a firewall. NAT is used to save public IP addresses (all of your home IP addresses are condensed into one public IP address supplied by your ISP). It also provides some level of security. Your firewall decides what traffic can get into your home network.

The switch allows you to expand your wired network by giving you more ethernet ports that you can use. It switches which ports are communicating at one time at a very high speed.

I will not get into how each of these work, as it took me about 1.5 years of very intensive learning to understand networks in the way I do today.

Step 2: IP Addresses

Each device on a network has a unique IP address. In a home network, each IP address will most likely start with 192.168. This signifies that it is a private class C address. More than likely, the subnet mask (which tells you how "big" your network is) will be 255.255.255.0. This allows you 254 host addresses. Most home networks will have a default gateway address (your router's IP address) of 192.168.(1-254).1 or 192.168.(1-254).254. Many home networks will either use the 192.168.0.0 network or 192.168.1.0 network. Generally your router will have either the first usable address in the subnet, or the last usable address. This means that 90% of the time, your router's default IP address will either be 192.168.1.1, 192.168.1.254, 192.168.0.1, or 192.168.0.254.

Most routers will automatically assign each computer an IP address through a process called DHCP (Dynamic Host Configuration Protocol). When your computer joins the network, it basically sends out a message to every computer on the network that says "can anyone tell me what IP address I should use?", and the router will reply with the addressing information.

To find out what IP address is assigned to your computer, go to command prompt, type "ipconfig", and press enter. This will give you a display of all the settings for each network adapter on your computer.

It is also worth mentioning that this is examples of IPv4 addresses. Some large companies are now switching over to IPv6, which is completely different from IPv4, but that shouldn't affect your home network. (At least not any time soon.)

Step 3: DNS Servers

IP addresses are the addresses that computers use to communicate, so many people ask me "how is it that when we type in a URL such as http://www.google.com that it knows where to go?" The answer is that in addition to IP addresses on computers, we also set DNS (Domain Name System) servers. These servers translate the domain names we type in to our browser into IP addresses, and tell our computer what IP address to use.

Step 4: Conclusion

So that's how your network works. Your computer get's a unique IP address, it sends data to the router, which sends it to the modem, which sends it to the ISP, which sends it to it's final destination. To find a URL, your computer sends a request packet to the DNS server, which responds with the IP address, which your computer uses to find the web page.

You can see a topology in the picture.

If you have any questions, feel free to comment below. Please note that this is not meant to be an in-depth exploration of networking, it is just a guide to give people a basic understanding of how their network works in order to help them troubleshoot.