Difference between IPv4 and IPv6

March 7, 2014
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• Networking 101

This article is intended to show difference between IPv4 and IPv6. It introduces the list of new features that IPv6 is offering.

When you see IPv6 address it is easy to notice how differently it is written. While IPv4 is written in a form of four decimal numbers separated by a period, the IPv6 is having eight hexadecimal numbers separated by the colons. Representation for the computer is in binary form, but it is written in decimal/hexadecimal form for ease of the user.

The reason for such big difference between IPs is in their size. IPv4 is representing four four-bit fields, while IPv6 offer eight 16-bit fields. This results in significant increase of available IP-addresses. The amount of IPs is 2^128. This enormous amount of IPs allows to assign unique address to every network interface. Since today almost every device has its network interface (even some refrigerators) the IPv6 offers big advantage over IPv4.

Table 1. IPv4 and IPv6 comparison.

From Table 1 we could see the examples of both types of IPs. Since many IPv6 could contain multiple zero value fields, there are two ways of shorting/collapsing the written representation.

• Remove all the leading zeros if they are before other hexadecimal digit. That makes value 002D to be written as 2D (Example 1. FE80:0:0:2D:202:B3FF:FE1E:8329)

• All multiple zero value fields are replaced with double colon (Example 2. FE80::2D:202:B3FF:FE1E:8329)

Note that second method can be applied only once per IP, otherwise it might be impossible to guess the amount of fields replaced by :: sign (Example 3. 2:0:0:7:8:0:0:F can be either 2::7:8:0:0:F or 2:0:0:7:8::F, but not 2::7:8::F)

IPv6 could be different types intended for different purposes. Some IPs intend to tell the type of recipient. Most common type of IP is the unicast address. It is usually assigned to the workstation network interface card or to some single end device. One of the most commonly used unicast addresses is the loopback address. As one may know, IPv4 loopback address is the 127.0.0.1. For the IPv6 this value has changed to the 0:0:0:0:0:0:0:1 or ::1.

Another type of address is the multicast address. It is assigned to multiple devices and is used for sending the same data to the same recipients at the same time. Basically it is P2MP solution, similar to broadcast transmission in IPv4.

Next type, anycast address type can be assigned to the networking equipment that is not host. All the routers in the anycast group share the same IP and if it is requested, the response is sent by any available router. This allows faster transmission, since the data can be transmitted by any available router, instead of waiting for some specific router to become available.

Every IP of the IPv6 is having Format Prefix that is identifying the type of the address. Types of the Format Prefixes can be found in Table 2.

Table 2. Types of Format Prefixes.

All modern systems are able to operate with IPv4 and IPv6. Ability of network to do that is called a dual-stack approach. Usage of dual-stack is popular due to the fact that not all the companies switched to IPv6 yet.