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 this type of address in simple terms, the differences between IPv4 vs. IPv6, and help you figure out the IP address of any device within your local network.
Dong’s note: I originally published this post on Feb 15, 2018, and last updated it on May 7, 2025, 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 a network, be it the Internet or 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 “dongknowstech.com” or “Server”, is simply a helpful way to mask that address so that we humans can remember it.
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 (in your home network, that’s your router). In other words, you can’t have two devices sharing one IP address in the same network (same subnet, to be specific) and expect them to work correctly, if at all.
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 the 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 an IPv6 address explicitly). The truth is that 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—unique addresses. Technically, that’s also the maximum number of devices in the same network.
While that seems like a lot, there are about 10 billion people globally, and one of us can have more than one device. As a result, IPv4 inevitably runs out of addressing space at some point. Or does it?
That brings us to a few terms that seemingly have nothing to do with those numbers mentioned above.
To conserve the addresses, IPv4 is available at two levels: Wide Area Network (WAN) and Local Area Network (LAN). They are equally important.
It’s the WAN level where the above-mentioned maximum number of IPv4 addresses strictly applies. Specifically, again, we can’t have more than 4,294,967,296 WAN IP addresses, also known as public IP addresses. In other words, that’s the total number of unique devices that can connect to the Internet at any given time using IPv4. That has always been the case, and it’s where IPv4 has been limited.
However, we need to connect many more devices than that, and we have done so for years with IPv4. That’s where the LAN level of networking comes into play. It’s a separate sub-level (or subnet) that’s not part of the WAN level.
Specifically, as you’re reading this, your router is the only device that has the unique public WAN IP assigned to you by the service provider, allowing it to connect to the Internet.
After that, an essential job of a router is to create a sub-level LAN network with a different set of local private IP addresses for the rest of the devices within your home network, such as computers, smart TVs, phones, or tablets. Among those is the device you’re using to surf this website right now.
The function that shares the Internet connection of one unique WAN IP address to many devices, each with its own unique LAN IP address, is called network address translation or NAT. As a result, the majority of Internet-connected devices don’t have a WAN IPv4 address of their own.
Let’s find out more about the details of NAT.
NAT: DHCP, IP pool, and lease time
As mentioned, the router creates a local IP network. It does that via a built-in Dynamic Host Configuration Protocol (DHCP) server.
All routers come with a simplified built-in DHCP server, 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.
Extra on IP lease time
The IP lease time is the window of time the router will keep an IP for a particular device, even if the device is no longer connected. The IP will not be available to any other client during this period.
This period starts when the device first connects and won’t change until the release time runs out or when you restart the router, whichever comes first. When a router restarts, all devices reconnect with a new lease.
The lease time is used in seconds. By default, most routers set it at 24 hours (86400 seconds), which is fine for most cases. But if you have an environment where you want the IP to become available faster, such as when you have a lot of devices for the IP pool, you can and should use a shorter lease time.
However, setting a lease too short can cause a router to overwork since it might have to renegotiate a new connection (and a new lease) for active clients. Generally, setting the lease time shorter than a few hours is not a good idea.
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 far in the future
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 indefinitely in the future. Additionally, many existing IPv4-only devices will last for ages 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 hundred 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.
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
- Click on the Start button, type in cmd, and then press Enter. The Command Prompt will appear.
- 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).
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.
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:
- Click on the Apple icon (top left) and then System Preferences.
- Find the Network icon and click on it.
- 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 know the IP address of a particular device, such as a printer or a NAS server.
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:
- Log in to the router’s web interface using its IP address. (Or open the mobile app for an app-operated router.)
- Navigate to the LAN section of the interface and then the DHCP server section.
- 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. Some routers have a network map that shows the connected clients and their IP addresses.
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.
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.
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 find out yours by Googling “what’s my IP address”.
To have a persistent WAN IP address, you need to pay for a static IP, which can be expensive—generally, only businesses need this. Most homes get a dynamic WAN IP, which occasionally changes.
Knowing your current WAN IP can come in handy when you want to access your home when out and about. To keep tabs on your changing dynamic WAN IP, you need to use a Dynamic DNS service. And this cool concept deserves a different post entirely.
