Did you know that your router has two IP addresses? We’ll show you how to find out what they are.
Private vs Public IP Addresses
Your home network (and most networks in general) consist of both private and public IP addresses. What’s the difference?
Public addresses can be used on the Internet, and private addresses can’t.
However, that’s not to say that private addresses don’t have their place. One of the main reasons private addresses exist, is because there are a limited number of public addresses.
In the current version of the Internet Protocol (IPv4), there are only about 4.3 billion public IP addresses. That may sound like a lot, but consider the fact that that number of addresses must provide internet access to every device on planet Earth, and suddenly its’ not such a big number.
There is a new version of the Internet Protocol coming (IPv6), which will drastically increase the number of public IP addresses available. However, global adoption of the new version has been very, very slow. It appears that the world will continue to use IPv4 for the foreseeable future.
Due to the fact that there is a shortage of pubic addresses, most people only get one public address from their ISP for their entire household. This addresses then goes on your router, and everything inside your home (computers, tablets, phones, game consoles, smart TV’s, thermostats, etc) gets a private address from your router instead of getting its’ own public address.
Your router also gets one of these private addresses so it can communicate with the devices in your home. It then performs a function called Network Address Translation (NAT) to translate traffic to/from devices on your network to/from the Internet using a combination of its’ private and public addresses.
Without NAT, you would only be able to use the internet on one device at a time because you only have one public IP address. How inconvenient!
With NAT, it’s like your router is bi-lingual and is translating a conversation between two people that don’t speak the same language. Your router must speak both languages to ensure that communication between the two parties is successful.
In this case, the two “languages” are the routers’ public IP address and private IP address.
So, your router is actually using two IP addresses at all times. It uses its’ public IP to communicate with devices on the Internet, and it uses its’ private IP to communicate with devices on your home network.
How do you tell the difference between public and private addresses?
Public and private addresses share the same format – four numbers (0 through 255) separated by three dots, such as 192.168.0.1.
Since they look the same, is there a way to tell if an address is public or private just by looking at it?
Turns out the answer is yes. There is a standard (RFC1918) that defines IP addresses that are reserved as private. They are:
Pretty much everything outside of these reserved ranges is public.
So, if you see an IP address beginning with 10, 172, or 192, chances are good that it is a private address. If it begins with any other number, it is a public IP address.
Why do you need your routers’ IP address?
Here are just a few reasons why you would need to know your routers’ IP addresses:
Reasons to need your private address
If you need to change the settings on your router – perhaps you want to change the name of your Wi-Fi network, modify your firewall settings, or change your Wi-Fi password. You will need to know your router’s private address in all of these cases so that you can login to your router and make the necessary changes.
- If you need to configure a device on your network with a static IP address – in this case the device won’t be configured automatically, so you’ll need to know your router’s private IP address – which will be entered into the ‘Default Gateway’ box in your computers’ IP address settings.
Reasons to need your public address
- If you need to access your home network remotely over the Internet – Maybe you are wanting to set up remote desktop to access your home computer from the office. Or, perhaps you are wanting to monitor a security camera in your home while you are on vacation.
- If you are hosting a server of some type – Perhaps you are running a file server or a game server – you will need to know your public IP address so that you can give it out to someone that would need to access your server remotely.
How to find your routers’ private IP:
Note: The vast majority of consumer-grade routers will use either 192.168.0.1 or 192.168.1.1 as their private address. Unless your router has been set up with a custom configuration, it is highly likely that one of these IP addresses will be assigned to your router.
Windows XP/Windows 7/Windows 10
- Click on the Start Menu (or press the ‘Windows’ key on your keyboard)
- Type ‘cmd’ (abbreviation for “command prompt”)
- Press ‘Enter’
- A black command prompt box will appear. Type in the word ‘ipconfig’ and press enter.
You will see a bunch of information scroll by and may have to scroll back up a bit to find what you are looking for – which is the Default Gateway IP address of your current network connection. In the example above, it is 192.168.1.1.
The default gateway is the address that your computer sends data to if it needs to go out to the Internet. This is the private IP address of your router.
- Click on the ‘Apple’ menu in the top left corner of your screen
- Select ‘System Preferences’
- From the System Preferences menu, click on the ‘Network’ icon
- Select your active network adapter on the left side
You will see IP address information appear on the right side. Look for the section that shows ‘Router:’.
This is the address that your computer sends data to if it needs to go out to the Internet. This is the private IP address of your router.
How to find your routers’ public IP:
This one is pretty easy. From any device on your home network, you just need to check a website that will retrieve the public IP address your traffic is coming from and report it back to you.
There are countless free sites out there that provide this service. Here are a few:
Google – Simply run a search with the words ‘What is my IP’ and Google will tell you.
Andrew Namder is an experienced Network Engineer with 20+ years of experience in IT. He loves technology in general, but is truly passionate about computer networking and sharing his knowledge with others. He is a Cisco Certified Network Professional (CCNP) and is working towards achieving the coveted CCIE certification. He can be reached at firstname.lastname@example.org.