Networking 101: What is an Internet Protocol (IP) address?

Internet Protocol (IP) technology was developed in the 1970s to support some of the earliest research computer networks. Today, IP has also become a worldwide standard for home and business networks. Our network routers, web browsers, email programs, instant messaging software – they all rely on IP or other network protocols layered over IP.

Today there are two versions of IP technology. Traditional home computer networks use IP version 4 (IPv4), but some other networks, particularly those in educational and research institutions, have adopted the next-generation IP version 6 (IPv6).

IPv4 address notation

An IPv4 address consists of four bytes (32 bits). These bytes are also known as octets.

For readability reasons, humans typically work with IP addresses in a notation called dotted decimal . This notation places dots between each of the four numbers (octets) that make up an IP address.

For example, an IP address that computers see as:

  • 00001010 000000000000 00000000 00000001

It is written in dotted decimal as:


Because each byte contains 8 bits, each octet of an IP address has a value from a minimum of 0 to a maximum of 255. Therefore, the full range of IP addresses is from to 255.255 .255,255 . This represents a total of 4,294,967,296 possible IP addresses.

IPv6 address notation

IP addresses change significantly with IPv6. IPv6 addresses are 16 bytes (128 bits) long instead of four bytes (32 bits). This larger size means that IPv6 supports more than:

  • 300,000,000,000,000,000,000,000,000,000,000,000,000,000,000

directions possible! As an increasing number of cell phones and other consumer electronics expand their networking capabilities and require their own addresses, the smaller IPv4 address space will be exhausted and IPv6 will become mandatory.

IPv6 addresses are generally written as follows:

  • hhhhh:hhhh:hhhh:hhhh:hhhh:hhhhh:hhhh:hhhh

In this full notation , IPv6 byte pairs are separated by colons, and each byte in turn is represented as a pair of hexadecimal numbers, as in the following example:

  • E3D7:0000:0000:0000:0000:51F4:9BC8:C0A8:6420

As shown above, IPv6 addresses commonly contain many bytes with a value of zero. Shorthand notation in IPv6 removes these values ​​from the text representation (although the bytes are still present in the actual network address) as follows:

  • E3D7::51F4:9BC8:C0A8:6420

Finally, many IPv6 addresses are extensions of IPv4 addresses. In these cases, the rightmost four bytes of an IPv6 address (the rightmost two-byte pairs) can be rewritten in IPv4 notation. Convert the above example to mixed notation yields:

  • E3D7::51F4:9BC8:

IPv6 addresses can be written in any of the full, short, or mixed notations illustrated above.