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Network Bytes · Episode 3 · CCNA 1.6

What is an IP address?

Every device online has an address, just like your house. Here's how to read one.

Posted · About a 1 minute watch, 2 minute read · Take the quiz

An address for every device

Every device that talks on a network needs an address, so data sent to it ends up in the right place. On networks and the internet, that's the IP address (IP stands for Internet Protocol, the set of rules for addressing and delivering data).

Think of the mail. A letter without an address can't be delivered. Data is the same: no address, no delivery.

How to read one

The most common kind, called IPv4, is written as four numbers separated by dots:

192.168.1.25

Each of the four numbers can be anything from 0 to 255. Why 255? Behind the scenes an IPv4 address is 32 bits (ones and zeros), split into four groups of 8 bits. Eight bits can count 256 different values, from 0 up to 255.

The address has two parts:

  • The first part names the network, like the street. In 192.168.1.25, that's usually 192.168.1.
  • The last part names the device on that network, like the house number. Here, that's 25.

Every device on the same home network shares the "street" part and gets its own "house number."

Where do addresses come from?

You almost never type one in yourself. When your phone joins your Wi-Fi, your router hands it an address automatically and remembers it for a while. That's called a lease. Leave home and come back tomorrow, and your phone may get a different address. Addresses handed out this way are called dynamic. Addresses that are set by hand and never change, which servers and printers often use, are called static.

Try it yourself

Open your phone's Wi-Fi settings and tap the network you're connected to. Look for IP address. It will probably start with 192.168 or 10., which are ranges set aside for home and office networks. Why those numbers show up everywhere is a whole lesson of its own, coming soon in this series.

Good to know

  • This lesson covers IPv4. There's a newer, much longer kind of address called IPv6, made because the world was running out of IPv4 addresses. It gets its own episode later in the series.
  • "First part network, last part device" is a simplification. The exact split is set by something called a subnet mask, which we'll cover when we get to subnetting.
  • The automatic hand-out is done by a service called DHCP, which also gets its own episode.

For CCNA learners

This lines up with CCNA 200-301 exam topic 1.6, configure and verify IPv4 addressing and subnetting. For now, get comfortable reading an address as four numbers from 0 to 255, with a network part and a device part.

Test your knowledge

Quick quiz: What is an IP address?

4 multiple-choice questions. Pick one answer for each, then check how you did.

1What does an IP address do?
2Which of these is a valid IPv4 address?
3On a home network, which part of 192.168.1.25 usually names the device?
4How does your phone usually get its IP address when it joins Wi-Fi?

Sources

Video transcript

Every device on the internet has an address, just like your house.

It's called an IP address. It tells the network where to deliver your data, the same way a street address tells the mail carrier where to drop off a letter.

A common type looks like this: four numbers separated by dots, like 192.168.1.25. Each number goes from 0 to 255. The first part usually names the network, like your street. The last part names the device, like your house number.

You almost never type one yourself. When your phone joins your Wi-Fi, the router hands it an address automatically. Leave and come back tomorrow, and you might get a different one.

No address, no delivery. That's why every device online needs one.

That's your bite. Next: the second address your device has, built in at the factory.