IP Address Explained: What It Is and How to Quickly Figure out Yours

If you've ever tried troubleshooting your home network or setting up a new router, you must have heard of "IP address" or "IP" for short. This post will explain more—in simple terms—about this type of address, IPv4 vs. IPv6, and help you find out yours at any given time.

Dong's note: I originally published this post on Feb 15, 2018, and last updated it on May 6, 2023, to add relevant information.

What is an IP address?

IP stands for Internet protocol. IP addresses are how devices identify themselves and talk to one another over the Internet or within a local network.

When you surf a website or browse a network computer, you access a particular IP address. A meaningful domain or computer name—such as dongknows.com or Server—is just a helpful way to mask that address so that we humans can remember it.

By the way, binding an IP address with a meaningful name is the job of a DNS server.

A device can't get connected if it doesn't have an IP address, which is uniquely assigned to each network member by a DHCP server (often, that's your router). In other words, you can't have two devices sharing one IP address in the same network and expect them to work correctly, if at all.

To avoid an IP conflict, refrain from manually assigning a static address to a device unless you can keep track of the addresses manually.

Within a local network, generally, the IP address of each member device remains the same for the duration it is on and connected. When you restart the device, its IP address might change unless you choose to reserve the same address for it by binding the IP with the device's MAC Address.

IPv4 vs. IPv6

There are two versions of Internet protocol: IPv4 and IPv6. The former is the most popular and generally the default connotation of an IP address. (You'll need to call the latter as IPv6 address explicitly). The truth is the popularity of IPv4 is why we need IPv6.

While IPv6 is newer and has been available for a few years, generally, for the most part, we're still dealing primarily with IPv4 now and long in the future, if not forever.

Internet protocol version four (IPv4)

IPv4 uses a 32-bit pool of addresses. As a result, a typical IPv4 address consists of four groups of three-digit numbers with a dot (.) in between, like this one: 192.168.010.002

You can omit the leading zeros in each group in an IP address, but each group must retain at least one digit. That said, the address above usually appears as 192.168.10.2

When you change a number, we have a new address, so mathematically, IPv4 can produce 4,294,967,296—four billion and then some—addresses.

While that seems like a lot, there are about 10 billion people globally, and one of us can have more than one device. If used at one level, IPv4 inevitably run out of addressing space at some point, if not already.

And that brings us to a few terms that seemingly have nothing to do with those numbers mentioned above.

WAN vs. LAN vs. NAT

To conserve the addresses, IPv4 is available at two levels: Wide Area Network (WAN) and Local Area Network (LAN).

At the WAN (or Internet) level, the address is always unique at any given time. For example, each website has a unique WAN IP address.

At your home, as you're reading this, chances are your router has your WAN IP. The router then creates a sub-level LAN network with a different set of local (or private) IP addresses for other devices, such as computers, smart TVs, phones, or tablets. Among those is the device you're using to surf this website right now.

Effectively, this allows multiple devices to access the Internet via a single WAN (or public) IP address instead of each having a WAN IP of its own. The router does that via network address translation or NAT.

DHCP, IP pool, and lease time

In your home, other than the router, which gets the public IP address, the rest of the devices use LAN IP addresses that are unique only within the home network.

These local addresses are given out by a local Dynamic Host Configuration Protocol (DHCP) server. All routers come with a simple version of this server built-in, which is enough for most home networks. (A large network might have a dedicated computer as its advanced DHCP server.)

This server creates an IP subnetwork separate from the public WAN network and distributes addresses to all devices connected to the router. The number of addresses, called the IP pool, determines how many devices can be in the same local network at a time—it's a way to control the maximum number of devices in a network.

Generally, by the default configuration, a home router can host up to 253 devices, determined by the value of the IP Pool Starting Address and IP Pool Ending Address, as shown in the screenshot above. Note that the wording of these two settings might vary slightly between networking vendors.

When a device connects to a network, it gets a unique local IP address and can hold that address for a fixed amount of time, called the "lease time." When the lease time expires, its IP address will be reassigned, and it might remain the same or not. Lease time is generally measured in seconds and is often set to be one day by default. When a device disconnects, the IP might still be held for it until the lease time expires.

IP address assignment: Dynamic vs. manual

Note, though, that this address pool is not super strict and only applies to clients that get an IP address dynamically via the router's DHCP server function, which happens right after you plug a cable into a device or enter the Wi-Fi password. It doesn't affect manually assigned addresses.

For example, if you set the IP pool in the 192.168.2.100 and 192.168.2.200 range, you can manually set the IP of a client to 192.168.2.99. That client will still connect to the router successfully as long as there's no other device already with that IP address.

Unless there's a specific reason, it's a good idea not to assign an IP manually, which is quite a pain to do anyway. If you need to ensure a device always gets the same IP address, you can use the router's IP reservation feature instead.

IPv4 will be relevant for a long time

Thanks to the NAT function, you can have two routers with the same local IP subnetwork at two different locations, such as a home and an office. That is possible because the two are "shielded" behind each router's unique WAN IP address.

This shielding also has another bonus. Devices connected to a router are behind a layer of protection from the outside world. Depending on the router in use and how you configure it, you can keep the entire network safe from identity thieves and other online threats.

The use of NAT is so effective that the global IPv4 address pool will suffice for a very long time in the future.

Additionally, many existing IPv4-only devices will last ages more and need to be supported.

So, IPv4 is not going away anytime soon, if at all. In any case, you can always choose to use it within your local network. But we still need something more robust, and that's where IPv6 comes into play.

Internet protocol version six (IPv6)

IPv6 uses a much larger 128-bit pool of addresses. A typical IPv6 address includes 8 groups of four characters (numbers or letters), divided by colons (:) and looks like this: 2001:0cd8:85e6:0000:0000:8e2c:0450:8733 or 2001:cd8:85e6:0:0:8e2c:450:8733 (leading zeros can be omitted).

While still finite, the total number of IPv6 addresses is exponentially higher than IPv4's.

Specially, we get the following total of IPv6 addresses:

340,282,366,920,938,463,463,374,607,431,768,211,456

(That's 340 trillion trillion trillion and then a couple of hundreds of trillion trillion more.)

At this level, it's safe to say we'll never run out of addressing space. That's great, but it can also bring about some privacy concerns. IPv6 means there's no need to conserve addresses anymore.

IPv6 and privacy concerns

Among other things, the IPv6 address assigned to each device at any given time can now be unique globally—universally, in fact. In other words, IPv6 addresses are generally always the WAN addresses.

Consequently, when your computer connects to the Internet using IPv6, it's exposed to the outside world. Thus, folks on the other end—like the website you visit—can trace back directly to the device instead of the router, as in the case of IPv4.

As a result, they can potentially tie certain online activities to a specific user. It's not that easy, and there are ways to minimize the risks—there's no need to get all worried—but still, the unique IP can imply a lot of things.

Currently, all home networks still use IPv4, with some also using IPv6 alongside. At the local level, most devices can have an IPv4 and an IPv6 address simultaneously. Most home routers support IPv6, but at the WAN level, very few Internet service providers use this new protocol exclusively.

You can usually choose to disable IPv6 at the router level or an individual device, and you should do the former if you don't want to deal with the new protocol or have privacy concerns.

How to find out your local IP addresses

Again, a local IP address belongs to a device within your home network, and we're talking mainly about IPv4 here. By the way, you generally can change the scheme of your local IPs via your router's interface.

How to find out the IP address of a Windows computer

1. Click on the Start button, type in cmd then press Enter. The Command Prompt will appear.
2. Type in ipconfig or ipconfig /all then press Enter. (The latter command reveals more information.)

Now, you will see your computer's local IP address (both IPv4 and IPv6) and your router's default gateway address. By the way, if you use the ipconfig /all command, you'll also see the MAC address (shown as the Physical Address).

Pro tip: Opening the Gateway IP address in a browser (like Chrome) will take you to your router's web interface (most routers have one). The interface can, among other things, be used to change your network's IP settings and find out the IP address of all connected clients in a network—more blow.

How to find out the IP address of a Mac computer

For Wi-Fi users:

Click on the Wi-Fi icon (top right) while holding down the Option key. You will see a menu with loads of information about the connection, including the IP addresses of your computer and the router.

If your Mac connects via a network cable, then do this:

1. Click on the Apple icon (top left) and then System Preferences.
2. Find the Network icon and click on it.
3. Click on the current connection. Here you'll find the information you need.

How to find out the IP address of any device in a local network

This part applies to a network with multiple connected devices, and you want to find out the IP address of any particular one among them.

This trick is helpful when you need to configure a device—be it a printer, an access point, or an IP camera—using the computer you are using. It's also useful when you want to know the IP of another computer in the network that you're not using.

To figure out the IP address of another device in the network, you need to have access to the network's DHCP server—in most cases, that's the router. Here are the steps:

1. Log in to the router's web interface using its IP address—see the Pro-tip above.
2. Navigate to the LAN section of the interface and then the DHCP server section. Some routers have a network map that shows the connected clients and their IP addresses.
3. Here, you'll see the list of connected clients. Most of the time, they have their names listed. If not, you can always find out which one is which by their MAC address.

Knowing a device's IP means you can access it via the address. If the device has a web interface, most printers and Wi-Fi access points do, and you can open this interface via its IP address.

Extra: When and how to reserve an IP address for a device

Reserving an IP address (or a DHCP address) binds a device's MAC address with an IP address. From then on, the router will keep that particular IP for that specific MAC address. So, every time the device connects to the network, it will get that same IP address.

This setting is helpful in situations where you don't want the device's IP to change. Examples are when you use a network printer, a network security camera, or a server of any kind. When the IP changes, the application you've set up with the particular device might not work anymore. It's always so in the case of port-forwarding.

While you don't need to reserve the IP for all connected clients, it doesn't hurt if you do so, either, as long as you remember to remove the reservation when a client is no longer part of the network.

Note that generally, a router can only keep track of so many reserved IP addresses—the number ranges from 8 to 128. If you want more devices to have a static local IP address, manual IP assignment is the way to go. In this case, in a standard setup, you can have all 253 local devices with their static IP.

The steps to make an IP reservation vary from one web interface to another, but you can almost always do that at the place where you can view the list of connected clients or the network map.

Most home routers—those from Asus, TP-Link, D-Link, Netgear, and Synology—allow you to do that via a click. With others, you might have to enter the MAC address and the IP address manually.

Final notes on the WAN IP address

The WAN IP address is the unique address that represents your entire home network to the Internet. For this reason, it's known as your public IP address. You can instantly look up your  WAN IP address at the top of this post. You can also Google "What's my IP."

Generally, your service provider assigns the WAN IP address to your home router (via the modem), and you can't change it.

Note that this public address tends to change occasionally unless you pay for an expensive static IP.

That said, you can't just write it down and expect to be able to dial home when you want. To keep tabs on your WAN IP when you're away from home, you need to use a Dynamic DNS service, and that deserves a different post entirely.