If you’ve ever tried troubleshooting your home network or setting up a new router, you must have heard of IP address. (If not, click on the Go button above, and you will immediately see an IP address at the lower-left corner of the test screen. It’s your WAN IP address by the way.)
This post will explain more — in layman’s terms — about this type of address, IPv4 vs. IPv6, and help you find out yours at any given time.
What is an IP address
IP stands for Internet protocol. IP addresses are how devices identify themselves and talk 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 IP address so that we humans can remember. 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 member of a network by a DHCP server (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 IP address to a device.)
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 IP address for it, by binding the IP address with the device’s MAC Address.
IPv4 vs. IPv6
There are two versions of Internet protocol, IPv4 and IPv6, with the former being the most popular and generally the default connotation of an IP address. (You’ll need to call the latter an IPv6 address explicitly). The truth is, the popularity of IPv4 is the reason why we need IPv6.
Though IPv6 is newer and has been available for a few years. Generally, though, for the most part, we’re still dealing mostly with IPv4, now and long in the future.
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
In an IP address, you can omit the leading zeros in each group, but each group must retain at least one digit. That said, the IP 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 — that is four billion and then some — addresses. While that seems like a lot, there are about 10 billion people in the world, and one of us can have more than one device. It’s quite inevitable that at some point, IPv4 will run out of addressing space.
Extra: WAN vs. LAN vs. NAT
To conserve the addresses, IPv4 is used 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. Generally, each website as a WAN IP address. At your home, your router (or gateway) has your WAN IP address — the one you found out on top of this post.
The router then creates a sub-level LAN network with a different set of local (or private) IP addresses for other devices, like your computers or your tablets, to use.
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 a function called network address translation, or NAT.
That said, in your home, other than the router, the rest of the devices use LAN IP addresses that are unique only within the home network. So you might find a computer at home that has the same LAN IP address as another at your friend’s. This duplication is possible because the two are “shielded” behind the unique WAN IP address of each home’s router.
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 thief and other online threats.
By the way, the use of NAT is so effective that I believe IPv4’s address pool will suffice for a very long time in the future. That’s not to mention many existing IPv4-only devices will last many many years more and need to be supported. So IPv4 is not going away anytime soon. But, still, we need something more robust, and that’s the slot IPv6 fills.
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, you can get 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 — addresses out of IPv6.
At this level, it’s safe to say we’ll never run out of addressing space. And that’s great but can also bring about some privacy concerns. The reason is with IPv6 there’s no need to conserve the addresses anymore.
Extra: 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 it, instead of the router, like the case of IPv4. As a result, among other things, they can potentially tie certain online activities to a specific user. And that implies a lot of things.
Currently, all home networks still use IPv4 with some also using IPv6 alongside. Most home routers support IPv6, but only a few service providers support this new protocol. Most of the time, you can choose to disable IPv6 at the router or an individual device.
How to find out your local IP addresses
Again, a local IP address is that of a device within your home network, and we’re talking mostly 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 then type in cmd 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 the local IP address (both IPv4 and IPv6) of your computer and the Default Gateway IP address, or your router’s. By the way, if you use the ipconfig /all command, you’ll also see the MAC address (shown as 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). Among other things, you can use the interface to change the IP settings of your network 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
If you have Wi-Fi, 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 computer IP address and that of the router.
If your Mac connects via a network cable then do this:
- Click on the Apple icon (top left) 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 configure that device — be it a printer or 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:
- Log in the router’s web interface using its IP address — see the Pro-tip above.
- 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.
- 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.
Once you have determined the IP address of a device, you can use it to access it. If the device has a web interface — most printers and Wi-Fi access points do — you can open this interface via its IP address.
Extra: When to reserve an IP address for a device
Reserving an IP address (or a DHCP address) is when you bind 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 the reserve the IP for all connected clients, it doesn’t hurt if you do so, either.
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 routers — like those from Asus, TP-Link, D-Link, Netgear, Synology — allow you to do that via a click. With others, you might have to enter the MAC address and the IP address manually.
More on 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. Or you can 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 in most cases, this public address tends to change once in a while, unless you pay for a static IP, which is expensive. 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.
Dong’s note: I originally published this post on Feb 15, 2018, and have updated it since to add relevant information.