An IP (Internet Protocol) Address is an alphanumeric label assigned to computers and other devices that connect to a network using an internet protocol. This address allows these devices to send and receive data over the internet.
Every device that is capable of connecting to the internet has a unique IP address. It’s similar to a home mailing address—by this unique address, information can get to the location specified.
End users don’t need to know the ins and outs of IP addresses. But in the same way a mailman needs to know more about mailing addresses, a network administrator or IT employee needs to know the technical details behind IP addresses for managing networks.
IP addresses are not random. They are mathematically produced and allocated by the Internet Assigned Numbers Authority.
How IP addresses work
The IP communicates using set guidelines to pass along information. Devices find, send, and exchange information with other connected devices using the IP. A device indirectly connects to the internet by first connecting to a network connected to the internet, which then grants the device access to the internet.
This network may be your home internet service provider (ISP), a company network, or a wireless network. At home, an IP address is assigned to your computer by your ISP, such as AT&T or Cox Communications. Your ISP assigns an IP address to your computer. The internet activity goes through it, and they route it back to you using the address.
When you travel outside your home, your IP address changes. When you connect to a different network, such as one from a coffee shop or at your work, you’re using a different and temporary IP address to connect to the internet.
How to read an IP address
There are two versions of the IP in use: IPv4 and IPv6. IPv4 used to be the standard version of IP addresses used for all devices. This version uses a 32-bit number format, meaning it’s a string of characters made up of 32 numbers. It can support a maximum of approximately 4.3 billion unique IP addresses. Due to the massive growth in devices connecting to the internet, the number of unique IPv4 addresses was eventually depleted.
IPv6 was developed as the new standard to alleviate this issue, the first IPv6 address being assigned in 1999. In IPv6, the IP address size is increased from 32-bits to 128-bit. Additionally, letters can be included along with numbers. This new version of IP address can theoretically support an infinite number of unique addresses.
For the purposes of this guide, we’ll define how to read both an IPv4 and an IPv6 address.
How to read an IPv4 address
An IPv4 address consists of 32 bits, limiting the address space to 4,294,967,296 possible unique addresses. This 32-bit number is written in decimal digits, formatted as four 8-bit (known as an octet) fields separated by periods. These octets create an addressing scheme that accommodates different network types. The five different classes of networks are A through E, which is addressed further below.
Each 8-bit field represents a byte of the IP address. Each number in the set can range from 0 to 255. This form of repensenting the bytes of an IP address is often referred to as the dotted-decimal format. This IPv4 address may be presented in various hexadecimal, octal, or binary representations. Consider the image below:
IP addresses are broken into two parts: network address and host address.
The network part specifies the unique number assigned to the network. It also identifies the class of network assigned. The amount of octets that define the network part versus the host part vary on the class of network. For example, in a Class A address, the network part is only the first octet while the rest is the host part. In a Class B address, the first two octets are the network part, while the remaining two are the host part.
The host is the part of the IP address that is assigned to each host. It uniquely identifies the machine on the network. For each host on a network, the network part of the address will be the same, but the host part will be different.
Subnetting is the process of dividing larger networking into smaller sub-networks (subnets).
An IP address identifies both a network and a unique interface on that network. A subnet mask is used by the IP to determine whether a host is on the local subnet or on a remote network.
It determines where the network part of an IP address ends and where the host part begins to identify which part of the IP address is reserved for the network and which part is available for use.
When an IP address is expressed in binary format (0s and 1s), any bit set to 1 means that the corresponding bit in the IP address is part of the network address. If the bit is set to 0, it’s part of the host address. The bits marking the subnet mask must be consecutive ones. Most subnet masks start with 255 and continue until the network mask ends. There are many online calculators available to calculate the subnet mask, taking out the manual mathematical work needed in finding the mask numbers.
Classes A through E
As mentioned above, IP addresses are divided into classes. The most common classes are classes A,B, and C. There are also classes D and E, but these aren’t used by end users. Each class has a different default subnet mask and can be identified by looking at the first octet of the IP address. The following table gives an overview:
How to read an IPv6 address
An IPv6 address has 128 bits (16 octets), providing up to 2128 addresses. Not only was IPv6 designed to provide a sufficient amount of IP addresses, but it also redesigned routing within the internet by providing more efficient aggregation of subnetworking routing prefixes. It provides the opportunity to separate the addressing infrastructure of a networking segment.
All modern desktop and enterprise server operating systems include native support for the IPv6 protocol, but it’s not yet widely used in devices such as residential routers, VoIP, and multimedia equipment.
IPv6 addresses are represented by eight sets of four hexadecimal digits with each set of numbers separated by a colon. These addresses can include both numerical and alphabetical digits. An example looks like the image below:
IPv6 addresses are also split into 2 equal parts: network and host. The first 64-bit network part is used for routing. The second 64-bit host part is an interface identifier used to identify a host’s network interface. A subnet mask is only used in IPv4, not IPv6. In addition, IPv6 does not implement classes.
IP address FAQ
What is a private IP address?
A private IP address is the identifier given to devices connected to a private network. These addresses are only accessible by devices inside a private network. Private IP addresses are not all unique, as there are only a limited number of devices connected to a network at any given time.
What is a public IP address?
A public IP address is the main address used for communicating between hosts and the global internet. This address is unique for all users. Public IP addresses come in two main varieties of their own: dynamic and static
What is a dynamic IP address?
Dynamic IP addresses change automatically and frequently. Most internet users are provided with a dynamic IP address from their ISP. The ISP buys a large chunk of IP addresses and automatically assigns one to each customer. They will then periodically reassign the customer a new IP address and recycle the old one.
This process is more secure for customers than keeping an IP address for a long period of time. It’s much harder to hack into a single device or network interface if the IP address keeps changing.
What is a static IP address?
Once a network assigns a static IP address, it remains the same. Most individual users and businesses don’t need a static IP address, but for businesses planning to host their own server, it’s necessary.
In maintaining your own server, having a static IP address ensures that any website or email address on it will be tied to consistent IP addresses.