Every device that connects to a network needs an address, and understanding the sections of an ip address is the key to understanding how that addressing works. An IP address is a numerical label that identifies a device on a network, and it is divided into sections that each carry a specific piece of information. In the most common version, IPv4, the address has four sections separated by dots. In the newer version, IPv6, the address has eight sections separated by colons. This guide explains both versions in plain language, describes what each section does, and shows how the sections work together to get data from one device to another. Everything here is general technical education about your own network: how addresses are structured, how to read them, and how to understand the settings on your own devices.
What the Sections of an IP Address Do
Think of an IP address the way you think of a postal address. A postal address has parts that narrow down the location step by step: the country, the city, the street, and finally the house number. An IP address works in the same way. Its sections divide the job of identifying a device into two broad parts: a network part, which identifies which network the device belongs to, and a host part, which identifies the individual device within that network. Routers use the network part to decide which direction to send data, and once the data reaches the right network, the host part directs it to the correct device.
The boundary between the network part and the host part is not fixed. It is set by a companion value called the subnet mask, which tells a device how many of the address sections belong to the network and how many belong to individual hosts. A small home network might use a mask that reserves the first three sections for the network and leaves the last section for devices, giving up to 254 usable device addresses. A large organisation might use a different mask that reserves fewer sections for the network and more for hosts, or the reverse, depending on how many separate networks and devices it needs. This flexibility is one of the reasons IP addressing has lasted so long: the same basic structure can serve a single household and a global corporation.
It is also important to distinguish between the two kinds of addresses you will meet on your own network. A private IP address is used inside a home or office network, and it is not directly reachable from the wider internet. A public IP address is the address your internet provider assigns to your connection as a whole, and it is the address the rest of the internet sees. Your router translates between the two, a process called network address translation, so that many devices at home can share a single public address. When you look at your own device settings, you will normally see a private address, which is exactly what you should expect.
The Sections of an IP Address in IPv4
An IPv4 address consists of 32 bits, written as four decimal numbers called octets, each ranging from 0 to 255, separated by dots. The word octet means eight, because each section represents eight bits of binary data. A typical example is 192.168.1.25, where 192, 168, 1, and 25 are the four octets. The first octet is the most significant, meaning it carries the broadest information, and each following octet narrows the location further, just like the parts of a postal address.
In a common home network, the first three octets identify the network, and the last octet identifies the device. In the example 192.168.1.25, the network portion is 192.168.1, and the host portion is 25, meaning the 25th device address on that network. The router itself usually takes the first address on the network, often ending in .1, and it hands out the remaining addresses to phones, laptops, televisions, and other devices automatically, using a service called DHCP. Because the addresses are assigned automatically, most home users never need to set them by hand, but understanding the structure makes troubleshooting much easier when something goes wrong.
Certain ranges of IPv4 addresses are reserved for private use and never appear on the public internet. The three private ranges are 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255. If the address shown on your own device falls inside one of these ranges, it is a private address on your own local network, and that is normal. Another special address worth knowing is 127.0.0.1, known as the loopback address, which always refers to the device itself and is used for testing software on your own machine. None of these addresses identifies anyone else or reveals anything about another person’s network; they are standard, public pieces of networking knowledge.
Subnet Masks and How Sections Are Divided
The subnet mask is the value that draws the line between the network sections and the host sections of an address. It is written in the same dotted form, and the most common home mask is 255.255.255.0. Each 255 means that the corresponding octet belongs entirely to the network part, and each 0 means that the octet belongs entirely to the host part. With the mask 255.255.255.0, therefore, the first three octets are the network and the last octet is the host, which matches the home example above.
Network engineers also write masks in a shorter form called CIDR notation, after Classless Inter-Domain Routing. In this notation, a slash followed by a number states how many bits belong to the network part. The mask 255.255.255.0 becomes /24, because 24 of the 32 bits are network bits. A /16 mask reserves 16 bits for the network and 16 for hosts, giving a much larger pool of device addresses, while a /25 mask splits a network into smaller subnets with fewer hosts each. CIDR notation is simply a compact way of writing the same information as a subnet mask, and you will see it often in router settings and technical guides.
Understanding masks matters because many connection problems are really mask problems. If two devices on the same network have different masks, they may disagree about which addresses are local and which are remote, and traffic between them can fail even though both devices appear to be connected. Checking that your own devices share the same network portion and the same mask is a sensible first step when your own home network misbehaves, and it is a task you can do entirely within your own settings, without touching anyone else’s equipment.
The Sections of an IP Address in IPv6
IPv4 provides roughly 4.3 billion unique addresses, which sounded inexhaustible in the 1970s but began to run short as the internet grew to billions of devices. IPv6 was created to solve that problem, and it uses 128 bits instead of 32, giving an effectively unlimited supply of addresses. An IPv6 address is written as eight groups of four hexadecimal digits, separated by colons, for example 2001:0db8:85a3:0000:0000:8a2e:0370:7334. Hexadecimal uses the digits 0 to 9 and the letters a to f, which allows each group to represent 16 bits compactly.
As with IPv4, the sections of an IPv6 address divide into a network part and a host part, but the division is usually simpler. The first four groups, 64 bits, typically identify the network, and the last four groups, 64 bits, identify the individual device, often generated automatically from the device itself. IPv6 also has shortening rules: leading zeros in a group can be dropped, and one run of consecutive all-zero groups can be replaced by a double colon. The example above can therefore be written more compactly as 2001:db8:85a3::8a2e:370:7334. These rules make IPv6 addresses easier to read, though they still look unfamiliar to readers used to dotted IPv4 addresses.
Most home users already have IPv6 available without realising it, because modern routers and internet providers often assign both an IPv4 and an IPv6 address to the same connection, a setup called dual-stack. Your own devices may therefore show two addresses side by side in their network settings. There is no need to choose between them: your devices and your provider handle the choice automatically, using IPv6 where it is available and falling back to IPv4 where it is not. Knowing that both exist, and that both follow the same network-and-host logic, removes much of the mystery from network settings pages.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Total length | 32 bits | 128 bits |
| Number of sections | 4 octets | 8 groups |
| Separator | Dots | Colons |
| Number style | Decimal, 0 to 255 | Hexadecimal |
| Example | 192.168.1.25 | 2001:db8:85a3::8a2e:370:7334 |
| Typical network part | First 3 octets at home | First 4 groups |
| Typical host part | Last octet | Last 4 groups |
Reading Your Own Network Settings
You can view the IP address of your own device in its network settings, and doing so is a useful way to make the ideas in this guide concrete. On a computer, the network settings page shows your own IP address, your subnet mask, and your gateway, which is the address of your own router. On a phone, the same information appears in the details page of the Wi-Fi network you are connected to. Comparing the address shown on two of your own devices is instructive: the network sections should match, because both devices are on the same home network, while the host sections should differ, because each device has its own address.
If the network sections do not match between two of your own devices, they are probably connected to different networks, for example one on your home Wi-Fi and one on a mobile connection, or one on a main network and one on a guest network. If a device shows an address beginning with 169.254, it has failed to obtain an address automatically and has assigned itself a fallback address, which usually means it cannot reach your router. Both observations are made entirely about your own equipment, and both point to practical next steps: reconnecting to the right network, restarting your router, or checking that automatic address assignment is switched on.
A word of caution belongs here. This guide describes how to understand and manage your own network, and that is the proper scope for this knowledge. Looking up, probing, or attempting to identify someone else’s address or network is a different activity, with different implications, and it is not covered here. The skills in this article, reading your own settings, understanding your own subnet mask, and recognising your own private address range, are complete in themselves and are all most home users will ever need.
Frequently Asked Questions
How many sections does an IP address have?
An IPv4 address has four sections, called octets, separated by dots. An IPv6 address has eight sections, called groups, separated by colons. In both versions, the sections divide into a network part and a host part.
What is an octet in an IP address?
An octet is one of the four sections of an IPv4 address, representing eight bits of data and written as a decimal number from 0 to 255. The word octet refers to those eight bits.
What is the difference between the network part and the host part?
The network part identifies which network a device belongs to, and routers use it to direct traffic toward that network. The host part identifies the individual device within that network. The subnet mask sets the boundary between the two parts.
Why are there two versions, IPv4 and IPv6?
IPv4 has about 4.3 billion addresses, which is not enough for the modern internet. IPv6 uses 128-bit addresses, providing an effectively unlimited supply, and it is gradually being adopted alongside IPv4.
Conclusion
The sections of an ip address are not arbitrary numbers: they are a structured system in which each part has a job. In IPv4, four octets divide into a network portion and a host portion, with the subnet mask setting the boundary. In IPv6, eight hexadecimal groups do the same job on a vastly larger scale. Private ranges, loopback addresses, and gateway addresses all fit into this same framework, and once you can read your own network settings with this structure in mind, router pages and troubleshooting guides become far less intimidating. The postal analogy is a good one to carry away: the network part is the street, the host part is the house number, and together they make sure every message arrives at the right door. For related networking help, see our guide on Debian static IP address setup and our explainer on the command to know the IP address in Linux for your own machine.
