OSPF reserves the multicast addresses < tt > 224. 0. 0. 5 </ tt > for IPv4 or < tt > FF02 :: 5 </ tt > for IPv6 ( all SPF / link state routers, also known as < tt > AllSPFRouters </ tt >) and < tt > 224. 0. 0. 6 </ tt > for IPv4 or < tt > FF02 :: 6 </ tt > for IPv6 ( all Designated Routers, < tt > AllDRouters </ tt >), as specified in RFC 2328 and RFC 5340.

In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.

In practice, it is not uncommon to find an AX. 25 data link layer as the transport for some other network layer, such as IPv4, with TCP used on top of that.

This same method works on some, but not all, IPv4 anycast addresses.

IRC daemons support IPv4, and some also support IPv6.

The older IPv4 system of Internet Protocol addressing will become unable to supply new addresses some time in 2012 ; a new addressing scheme, IPv6, will remove the restriction but is not compatible with older equipment and ISP services.

For example, the domain name www. example. com translates to the addresses < tt > 192. 0. 43. 10 </ tt > ( IPv4 ) and < tt > 2620: 0: 2d0: 200 :: 10 </ tt > ( IPv6 ).

* IPv4 addresses allocated: 11, 777, 024 or 1, 646 per 1000 population ( April 2012 )

IP addresses are binary numbers, but they are usually stored in text files and displayed in human-readable notations, such as 172. 16. 254. 1 ( for IPv4 ), and 2001: db8: 0: 1234: 0: 567: 8: 1 ( for IPv6 ).

Because of its prevalence, the generic term IP address typically still refers to the addresses defined by IPv4.

In IPv4 an address consists of 32 bits which limits the address space to ( 2 < sup > 32 </ sup >) possible unique addresses.

IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots, e. g., 172. 16. 254. 1.

IPv6 was developed by the Internet Engineering Task Force ( IETF ) to deal with the long-anticipated problem of IPv4 running out of addresses.

IPv6 implements a new IP address system that allows for far more addresses to be assigned than is possible with IPv4, but as a result the two protocols are not compatible, complicating the transition to IPv6.

With the ever-increasing number of new devices being connected to the Internet, there is a need for more addresses than IPv4 can accommodate.

IPv6 uses 128-bit addresses, allowing for 2 < sup > 128 </ sup >, or approximately addresses — more than times as many as IPv4, which uses 32-bit addresses.

IPv4 allows for only 4, 294, 967, 296 unique addresses worldwide ( or less than one address per person alive in 2012 ), but IPv6 allows for around addresses per person — a number unlikely ever to run out.

In addition to offering more addresses, IPv6 also implements features not present in IPv4.

IPv4 addresses are typically displayed as four numbers, each in the range 0 to 255, or 8 bits per number, for a total of 32 bits.

Thus IPv4 provides an addressing capability of 2 < sup > 32 </ sup > or approximately 4. 3 billion addresses.

The last available top-level () blocks of 16 million IPv4 addresses were assigned in February 2011 by the Internet Assigned Numbers Authority ( IANA ) to the five Regional Internet registries ( RIRs ).

In addition, the IPv4 address space is poorly allocated, with approximately 14 % of all available addresses utilized.

The standard size of a subnet in IPv6 is 2 < sup > 64 </ sup > addresses, the square of the size of the entire IPv4 address space.

The IP address is represented as a name in reverse-ordered octet representation for IPv4, and reverse-ordered nibble representation for IPv6.

DHCP is used for IPv4 and IPv6.

While both versions serve much the same purpose, the details of the protocol for IPv4 and IPv6 are sufficiently different that they may be considered separate protocols.

Many worked to clarify the protocol as it gained popularity, and in 1997 RFC 2131 was released, and remains the standard for IPv4 networks.

ICMP for Internet Protocol version 4 ( IPv4 ) is also known as ICMPv4.

Some protocols, or families of protocols, have one or more SAPs assigned to them ; for example, IPv4 has a SAP value of hex 06.

This work includes coordination of the Internet Protocol address spaces ( IPv4 and IPv6 ) and assignment of address blocks to regional Internet registries, for maintaining registries of Internet protocol identifiers, and for the management of the top-level domain name space ( DNS root zone ), which includes the operation of root nameservers.

IPv4 is a connectionless protocol for use on packet-switched Link Layer networks ( e. g., Ethernet ).

IPv6 is intended to replace the older IPv4, which is still employed for the vast majority of Internet traffic as of 2012.

IPv6, like the most commonly used IPv4 ( as of 2012 ), is an Internet-layer protocol for packet-switched internetworking and provides end-to-end datagram transmission across multiple IP networks.

Address exhaustion was not initially a concern in IPv4 as this version was originally presumed to be an internal test within ARPA, and not intended for public use.

It is widely expected that the Internet will use IPv4 alongside IPv6 for the foreseeable future.

Renumbering an existing network for a new connectivity provider with different routing prefixes is a major effort with IPv4.

IPv6 multicast addressing shares common features and protocols with IPv4 multicast, but also provides changes and improvements by eliminating the need for certain protocols.

In the IPv4 address space certain address blocks are specially allocated or reserved for special uses such as loopback interfaces, private networks ( RFC 1918 ), and state-less autoconfiguration ( Zeroconf, RFC 3927 ) of interfaces.

For link-local addressing IPv4 uses the special block < tt > 169. 254. 0. 0 / 16 </ tt > as described in RFC 3927 while IPv6 hosts use the prefix < tt > fe80 ::/ 10 </ tt >.

Reverse DNS lookups for IPv4 addresses use a reverse IN-ADDR entry in the special domain < tt > in-addr. arpa </ tt >.

A later IETF document, Special-Use IPv4 Addresses ( RFC 3330 ) describes the usage of the IPv4 address block < tt > 127. 0. 0. 0 / 8 </ tt > for loopback purposes.

The type of service ( TOS ) field in the IPv4 header has had various purposes over the years, and has been defined in different ways by five RFCs.