Types of IPv4 Addresses 5 Special IPv4 Address Blocks

There are several blocks, or ranges, of IPv4 addresses reserved for several purposes. The IP address or Internet Protocol is a numerical label assigned to each device that is a phone, computer or smart tv connected to a computer network that uses the Internet Protocol for communication.

IPv4 is Internet Protocol version 4 the fourth version of the IP and was first put to use in 1983 at ARPANET in the USA the birthplace of the internet.

An IP address serves two main functions: Firstly network addressing where the network part location is identified and secondly the host interface or the actual origin of network communication.

But in this blog, the writeup is to introduce the types of IPv4 addresses and the 5 special IPv4 address blocks.

You can also read about IPv4 Address Class

5 Special IPv4 Address Blocks

127.0.0.0/8

This address block is assigned for use as the Internet host loopback address. A datagram sent by a higher-level protocol to an address anywhere within this block loops back inside the host.

This is ordinarily implemented using only 127.0.0.1/32 for loopback.

As described in [RFC1122], Section 3.2.1.3, addresses within the entire 127.0.0.0/8 block do not legitimately appear on any network anywhere.

169.254.0.0/16

This is the “link local” block. As described in [RFC3927], it is allocated for communication between hosts on a single link. Remember when you learnt about Windows DHCP and the APIPA (Automatic Private IP Addressing)

Hosts obtain these addresses by auto-configuration, such as when a DHCP server cannot be found.

172.16.0.0/12

Like 192.168.0.0/16, this type of IP address block is set aside for use in private networks. Its intended use is documented in [RFC1918].

As described in that RFC, addresses within this block do not legitimately appear in the public Internet.

These addresses can be used without any coordination with IANA or an Internet registry.

192.168.0.0/16

By far the most famous and default set by routers and network engineers when deploying a network.

Like 172.16.0.0/12, this block is set aside for use in private networks. Its intended use is documented in [RFC1918].

As described in that RFC, addresses within this block do not legitimately appear in the public Internet.

These addresses can be used without any coordination with IANA or an Internet registry.

224.0.0.0/4

This block, formerly known as the Class D address space, is allocated for use in IPv4 multicast address assignments.

The IANA guidelines for assignments from this space are described in [RFC3171].

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