IPv4 addresses look like tiny door numbers for the internet. They help devices find each other, send messages, play games, stream videos, and ask servers for cat pictures. But not every IPv4 address does the same job. Some are public. Some are private. Some are weird little special cases. Let’s sort them out without making your brain melt.
TLDR: IPv4 addresses come in different types, and each type has a special purpose. Public addresses work on the internet, while private addresses are used inside local networks. Some addresses are reserved for testing, loopback, broadcasts, or automatic setup. To match an IP description correctly, look at the number range and ask, “Where is this address meant to work?”
What Is an IPv4 Address?
An IPv4 address is a number used to identify a device on a network. It looks like this:
192.168.1.25
It has four parts. Each part is called an octet. Each octet can be from 0 to 255. So an IPv4 address is like a four-part name tag.
Think of it like a street address. Your laptop needs an address. Your phone needs one too. A router also has one. Without addresses, data packets would wander around like lost pizza delivery drivers.
Public IPv4 Addresses
A public IPv4 address is used on the open internet. It is unique across the world. If a website, server, or home router talks directly to the internet, it usually uses a public address.
Example:
- 8.8.8.8
- 1.1.1.1
- 93.184.216.34
These addresses can be reached from the internet, unless a firewall blocks them. When you visit a website, your traffic usually travels between public IP addresses.
How to match the description: If the description says reachable on the internet, globally unique, or assigned by an ISP, it is probably a public IPv4 address.
Private IPv4 Addresses
A private IPv4 address is used inside a local network. Your home Wi-Fi uses private addresses. Offices use them too. They are not routed directly on the public internet.
Private ranges are:
- 10.0.0.0 to 10.255.255.255
- 172.16.0.0 to 172.31.255.255
- 192.168.0.0 to 192.168.255.255
Example:
- 192.168.1.10
- 10.0.0.5
- 172.16.4.20
Your router often gives these addresses to your devices. Then the router uses something called NAT, or Network Address Translation, to help them share one public address.
How to match the description: If the description says used inside a home network, not routable on the internet, or local LAN address, choose private IPv4 address.
Loopback Addresses
A loopback address is a device talking to itself. Yes, computers talk to themselves. No, it is not strange. It is very useful.
The most famous loopback address is:
127.0.0.1
It is often called localhost. Developers use it to test websites, apps, and services on their own machine.
The full loopback range is:
127.0.0.0 to 127.255.255.255
How to match the description: If the description says used by a host to contact itself, localhost, or testing on the same machine, it means loopback.
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APIPA Addresses
APIPA stands for Automatic Private IP Addressing. That name sounds fancy. The idea is simple.
If a device cannot get an address from a DHCP server, it may give itself an APIPA address. It is like saying, “Fine, I will make my own name tag.”
The APIPA range is:
169.254.0.0 to 169.254.255.255
Example:
- 169.254.10.8
- 169.254.200.44
APIPA can allow devices on the same local link to communicate. But it usually means something went wrong with DHCP.
How to match the description: If the description says self assigned, DHCP failed, or automatic address in the 169.254 range, choose APIPA.
Broadcast Addresses
A broadcast address is used to send a message to all devices on a network. It is the network version of shouting, “Hey everyone!”
The most general broadcast address is:
255.255.255.255
This is called the limited broadcast address. It stays on the local network and does not travel across routers.
Networks can also have their own broadcast addresses. For example, in the network 192.168.1.0/24, the broadcast address is:
192.168.1.255
How to match the description: If the description says sent to all hosts, local network announcement, or all bits set in the host part, it is a broadcast address.
Network Addresses
A network address identifies a whole network, not one device. It is like the name of a street, not a house number.
Example:
192.168.1.0/24
Here, 192.168.1.0 is the network address. Devices on that network might use addresses like 192.168.1.10 or 192.168.1.50.
You usually do not assign the network address to a normal device.
How to match the description: If the description says identifies the subnet, first address in the range, or not assigned to a host, it is probably a network address.
Multicast Addresses
Multicast is for sending data to a group of devices. Not everyone gets the message. Only devices that joined the group do.
The IPv4 multicast range is:
224.0.0.0 to 239.255.255.255
Multicast is used for things like streaming, routing protocols, and service discovery.
How to match the description: If the description says one to many, group communication, or shows an address from 224.0.0.0/4, choose multicast.
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Reserved and Experimental Addresses
Some IPv4 addresses are reserved. That means they are set aside for special uses. You should not treat them like normal public addresses.
One important reserved block is:
240.0.0.0 to 255.255.255.254
This range is mostly reserved for future or experimental use. The address 255.255.255.255 is special because it is used for limited broadcast.
There are also documentation addresses. These are used in books, examples, and training materials. They are safe to show because they are not meant for real internet hosts.
- 192.0.2.0/24
- 198.51.100.0/24
- 203.0.113.0/24
How to match the description: If the description says used in examples, not for real hosts, or reserved for documentation, pick reserved or documentation address.
Quick Matching Cheat Sheet
Here is the simple version. Keep this nearby when you need to match IP address descriptions.
- Public: Works on the internet. Globally unique.
- Private: Used inside local networks. Ranges include 10.x.x.x, 172.16-31.x.x, and 192.168.x.x.
- Loopback: Device talks to itself. Usually 127.0.0.1.
- APIPA: Self assigned after DHCP fails. Starts with 169.254.
- Broadcast: Message to everyone on a network. Often ends in .255 for many subnets.
- Network address: Identifies the subnet itself. Often the first address in a range.
- Multicast: Sends to a group. Range is 224.0.0.0 to 239.255.255.255.
- Reserved: Special use, examples, or experiments.
A Tiny Trick for Exams
When you see an IPv4 address, do not panic. Look at the first number. Then check the range. Ask what the address is trying to do.
Is it trying to reach the internet? It may be public. Is it hiding inside a home network? It may be private. Is it talking to itself? Say hello to loopback. Did DHCP take a nap? That smells like APIPA.
IPv4 address types are not random monsters. They are more like labeled toy boxes. Once you know the labels, matching the descriptions becomes easy. And yes, even 255.255.255.255 has a job. It just likes to shout.