IP

IP address1. Short for Internet Protocol address, an IP or IP address is a number (example shown right) used to indicate the location of a computer or other device on a network using TCP/IP. These addresses are similar to those of your house; they allow data to reach the appropriate destination on a network and the Internet.

IPv4 vs. IPv6

As the Internet and technology evolve, there has been an increasing demand for IP addresses. To help meet the demand for IP addresses, there are two types of addresses used today, IPv4 and IPv6. Although you may only deal with an IPv4 address in your local home, school, or small office you should also be aware of IPv6 addresses for when you encounter them.

Example of an IPv4 address:

69.72.169.241

Example of an IPv4 address:

2601:681:4200:c5c0:516:f0bb:ac3b:46bd

IP address classes

With an IPv4 IP address there are five classes of available IP ranges: Class A, Class B, Class C, Class D and Class E, while only A, B, and C are commonly used. Each class allows for a range of valid IP addresses, shown in the following table.

Class Address Range Supports
Class A 1.0.0.1 to 126.255.255.254 Supports 16 million hosts on each of 127 networks.
Class B 128.1.0.1 to 191.255.255.254 Supports 65,000 hosts on each of 16,000 networks.
Class C 192.0.1.1 to 223.255.254.254 Supports 254 hosts on each of 2 million networks.
Class D 224.0.0.0 to 239.255.255.255 Reserved for multicast groups.
Class E 240.0.0.0 to 254.255.255.254 Reserved for future use, or Research and Development Purposes.

Ranges 127.x.x.x are reserved for the loopback or localhost, for example, 127.0.0.1 is the loopback address. Range 255.255.255.255 broadcasts to all hosts on the local network.

IP address breakdown

Every IP address is broken down into four sets of octets and translated into binary to represent the actual IP address. The below table is an example of the IP 255.255.255.255. If you are new to binary, we highly recommend reading our binary and hexadecimal conversions section to get a better understanding of what we're doing in the below charts.

IP: 255 255 255 255
Binary value: 11111111 11111111 11111111 11111111
Octet value: 8 8 8 8

For an example, let's break down the IP "166.70.10.23" in the following table. The first row contains the separate sections of the IP address, the second has binary values, and the third row shows how the binary value equals the section of the IP address.

IP: 166 70 10 23
Binary value: 10100110 01000110 00001010 00010111
Numerical value: 128+32+4+2=166 64+4+2=70 8+2=10 16+4+2+1=23

Automatically assigned addresses

There are IP addresses that are automatically assigned (dynamic allocation) when you set up a home network. These default addresses are what allow your computer and other network devices to communicate and broadcast information over your network. Below are the most commonly assigned default addresses for home networks.

192.168.1.0 0 is the automatically assigned network address.
192.168.1.1 1 is the commonly used address used as the gateway.
192.168.1.2 2 is also a commonly used address used for a gateway.
192.168.1.3 - 254 Addresses beyond 3 are assigned to computers and devices on the network.
192.168.1.255 255 is automatically assigned on most networks as the broadcast address.

If you have ever connected to your home network, you should be familiar with the gateway address or 192.168.1.1, which is the address you use to connect to your home network router to change its settings. Another common IP range that may be used is 10.0.0.3-254.

Getting an IP address

By default the router you use will assign each of your computers their own IP address, often using NAT to forward the data coming from those computers to outside networks such as the Internet. If you need to register an IP address that can be seen on the Internet, you must register through InterNIC or use a web host that can assign you addresses.

Anyone who connects to the Internet is assigned an IP address by their Internet Service Provider (ISP), which has registered a range of IP addresses. For example, let's assume your ISP is given 100 addresses, 109.145.93.150-250. In this range, the ISP owns addresses 109.145.93.150 to 109.145.93.250 and can assign any address in that range to its customers. So, all these addresses belong to your ISP until they are assigned to a customers computer. In the case of a dial-up connection, you are given a new IP address each time you dial into your ISP. With most broadband Internet service providers, you are always connected to the Internet your address rarely changes. It remains the same until the service provider requires otherwise.

Connecting to the Internet

The above picture is taken from our "How do computers connect to each other over the Internet?" document and gives a good overview of how a computer can talk to another computer over the Internet using an IP address.

Other IP address questions and answers

2. A Linux and Unix command that allows the user to configure their network settings. See the ip command page for further information.

Also see: Binary, CIDR, External IP address, ICANN, Internal IP address, Internet address, InterNIC, IP spoofing, IPv4, IPv6, Localhost, Netmask, Network terms, Ping, Protocol, Reserved address space, Static allocation, Subnet