IPAddress

IP versions

Two versions of the Internet Protocol (IP) are in use: IP Version 4 and IP Version 6.

IPV4 - 32 bits - 2³² possible unique addresses (each group contains 1 octet 8 bits) - 255.255.255.255 (dot)

IPV6 - 128 bits - 2¹²⁸ possible unique addresses (each group contains 2 octet 8 bits) - 2001:0db8:85a3:0000:0000:8a2e:0370:7334 (Semi colon)

IP version 4 addresses (IPV4)

In IPv4 an address consists of 32 bits which limits the address space to 4294967296 (2³²) possible unique addresses. IPv4 reserves some addresses for special purposes such as private networks (~18 million addresses) or multicast addresses (~270 million 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. Each part represents a group of 8 bits (octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.

IP version 6 addresses (IPV6)

The rapid exhaustion of IPv4 address space, despite conservation techniques, prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand the Internet's addressing capability. The permanent solution was deemed to be a redesign of the Internet Protocol itself. This next generation of the Internet Protocol, intended to replace IPv4 on the Internet, was eventually named Internet Protocol Version 6 (IPv6) in 1995. The address size was increased from 32 to 128 bits or 16 octets. This, even with a generous assignment of network blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space provides the potential for a maximum of 2¹²⁸, or about 3.403×1038

unique addresses.

Presentation

An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets). The groups are separated by colons (:). An example of an IPv6 address is

2001:0db8:85a3:0000:0000:8a2e:0370:7334.

The hexadecimal digits are case-insensitive when used, but should be represented in lower case.

The full representation of eight 4-digit groups may be simplified by several techniques, eliminating parts of the representation.

Leading zeroes

Leading zeroes in a group may be omitted, but each group must contain at least one hexadecimal digit. Thus, the example address may be written as:

2001:db8:85a3:0:0:8a2e:370:7334.

Groups of zeroes

Two or more consecutive groups of zero value may be replaced with a single empty group using two consecutive colons (::). Substitution may only be applied once in an address, because multiple occurrences would create an ambiguous representation. If more than one such substitution could be applied, the substitution that replaces the most groups must be used; if the number of groups are equal then the leftmost substitution must be used. With these rules, the example address is further simplified:

2001:db8:85a3::8a2e:370:7334

The localhost (loopback) address, 0:0:0:0:0:0:0:1, and the IPv6 unspecified address, 0:0:0:0:0:0:0:0, are reduced to ::1 and ::, respectively.

Dotted-quad notation

During the transition of the Internet from IPv4 to the IPv6 it is typical to operate in a mixed addressing environment, and for this purpose a special notation has been introduced to express IPv4-mapped and IPv4-compatible IPv6 addresses by writing the final 32 bits of an address in the familiar IPv4 dotted-quad notation. For example, the IPv4-mapped IPv6 address ::ffff:c000:280 is usually written as ::ffff:192.0.2.128, thus expressing clearly the original IPv4 address that was mapped to IPv6.

Unicast address format

Unicast and anycast addresses are typically composed of two logical parts: a 64-bit network prefix used for routing, and a 64-bit interface identifier used to identify a host's network interface.

The network prefix is contained in the most significant 64 bits of the address. The recommended allocation to end users is a 48-bit routing prefix. In this scenario, the 16 bits of the subnet id(entifier) field are available to the network administrator to define subnets within the given network. The 64-bit interface identifier is either automatically generated from the interface's MAC address using the modified EUI-64 format, obtained from a DHCPv6 server, automatically established randomly, or assigned manually.

A link-local address is also based on the interface identifier, but uses a different format for the network prefix.

Networks

An IPv6 network uses an address block that is a contiguous group of IPv6 addresses of a size that is a power of two. The leading set of bits of the addresses are identical for all hosts in a given network, and are called the network's address or routing prefix.

Network address ranges are written in CIDR notation. A network is denoted by the first address in the block (ending in all zeroes), a slash (/), and a decimal value equal to the size in bits of the prefix. For example, the network written as 2001:db8:1234::/48 starts at address 2001:db8:1234:0000:0000:0000:0000:0000 and ends at 2001:db8:1234:ffff:ffff:ffff:ffff:ffff.

The routing prefix of an interface address may be directly indicated with the address by CIDR notation. For example, the configuration of an interface with address 2001:db8:a::123 connected to subnet 2001:db8:a::/64 is written as 2001:db8:a::123/64.

Address block sizes

The size of a block of addresses is indicated simply by a slash (/) and the decimal size of the network prefix, without specifying which specific addresses are in the block. For instance, an address block with 48 bits in the prefix is indicated by /48. Such a block contains 2^{128 − 48} = 2⁸⁰ addresses. The smaller the size of the network prefix, the larger the block: a /21 block is 8 times larger than a /24 block.

So in case of 2001:db8:1234::/48 - 2001:db8:1234::/64 = 2¹⁶ addresses

Or (2^{128 − 48} = 2⁸⁰) - (2^{128 − 64} = 2⁶⁴⁾ addresses = 2¹⁶ addresses

Note : It means IPV6/decimal number (48, 64) shows the network prefix used for routing. These are fixed bits for a specific network and remaining bits (128-48) is going to be utilized for the address purpose.

So in above case 2001:db8:1234::/48 , "2001:db8:1234:" is the fix address for routing purpose and remaining 80 bits are going to be used for giving IPV6 address for the devices belongs to this network.

start from 2001:db8:1234:0000:0000:0000:0000:0000 and ends at 2001:db8:1234:ffff:ffff:ffff:ffff:ffff.

Similarly for 64

2001:db8:1234:3451::/64 , "2001:db8:1234:3451" is the fix address for routing purpose and remaining 64 bits are going to be used for giving IPV6 address for the devices belongs to this network.

start from 2001:db8:1234:3451:0000:0000:0000:0000 and ends at 2001:db8:1234:3451:ffff:ffff:ffff:ffff.

External Links:

1. IPv6 Certifications : http://ipv6.he.net/certification/?gclid=CLW-n861iqgCFQwjHAodICOUCQ

2. To know more about IPV6 install, configure, and use IPv6 applications on Linux machines : http://tldp.org/HOWTO/Linux+IPv6-HOWTO/

3. quick configuration guide for IPV6 : http://www.iitk.ac.in/cc/iitkipv6configuration.htm

My IPV6 Certification

http://ipv6.he.net/certification/cert-main.php

user id : manojsinghal258