IPv6 Tutorial
Internet Protocol version 6
Internet has been growing extremely fast so the IPv4 addresses are quickly approaching complete depletion.
Although many organizations already use Network Address Translators (NATs) to map multiple private
address spaces to a single public IP address but they have to face with other problems from NAT (the use of
the same private address, security…). Moreover, many other devices than PC & laptop are requiring an IP
address to go to the Internet. To solve these problems in long-term, a new version of the IP protocol
version 6 (IPv6) was created and developed.
IPv6 was created by the Internet Engineering Task Force (IETF), a standards body, as a replacement to IPv4 in 1998. So what happened with IPv5? IP Version 5 was defined for experimental reasons and never was deployed.
While IPv4 uses 32 bits to address the IP (provides approximately 232 = 4,294,967,296 unique addresses but in fact about 3.7 billion addresses are assignable because the IPv4 addressing system separates the addresses into classes and reserves addresses for multicasting, testing, and other specific uses), IPv6 uses up to 128 bits which provides 2128 addresses or approximately 3.4 * 1038 addresses. Well, maybe we should say it is extremely extremely extremely huge :)
IPv6 Address Types
A single interface may be assigned multiple IPv6 addresses of any type (unicast, anycast, multicast)
IPv6 address format
Format:
x:x:x:x:x:x:x:x– where x is a 16 bits hexadecimal field and x represents four hexadecimal digits.
An example of IPv6:
2001:0000:5723:0000:0000:D14E:DBCA:0764
There are:
+ 8 groups of 4 hexadecimal digits.
+ Each group represents 16 bits (4 hexa digits * 4 bit)
+ Separator is “:”
+ Hex digits are not case sensitive, so “DBCA” is same as “dbca” or “DBca”…
IPv6 (128-bit) address contains two parts:
+ The first 64-bits is known as the prefix. The prefix includes the network and subnet address. Because
addresses are allocated based on physical location, the prefix also includes global routing information. The
64-bit prefix is often referred to as the global routing prefix.
+ The last 64-bits is the interface ID. This is the unique address assigned to an interface.
Note: Addresses are assigned to interfaces (network connections), not to the host. Each interface can have
more than one IPv6 address.
Rules for abbreviating IPv6 Addresses:
+ Leading zeros in a field are optional
2001:0DA8:E800:0000:0260:3EFF:FE47:0001 can be written as
2001:DA8:E800:0:260:3EFF:FE47:1
+ Successive fields of 0 are represented as ::, but only once in an address:
2001:0DA8:E800:0000:0000:0000:0000:0001 -> 2001:DA8:E800::1
Other examples:
– FF02:0:0:0:0:0:0:1 => FF02::1
– 3FFE:0501:0008:0000:0260:97FF:FE40:EFAB = 3FFE:501:8:0:260:97FF:FE40:EFAB =
3FFE:501:8::260:97FF:FE40:EFAB
– 0:0:0:0:0:0:0:1 => ::1
– 0:0:0:0:0:0:0:0 => ::
IPv6 Addressing In Use
IPv6 uses the “/” notation to denote how many bits in the IPv6 address represent the subnet.
The full syntax of IPv6 is
where
+ ipv6-address is the 128-bit IPv6 address
+ /prefix-length is a decimal value representing how many of the left most contiguous bits of the address
comprise the prefix.
Let’s analyze an example:
2001:C:7:ABCD::1/64 is really
2001:000C:0007:ABCD:0000:0000:0000:0001/64
+ The first 64-bits 2001:000C:0007:ABCD is the address prefix
+ The last 64-bits 0000:0000:0000:0001 is the interface ID
+ /64 is the prefix length (/64 is well-known and also the prefix length in most cases)
In the next part, we will understand more about each prefix of an IPv6 address.
The Internet Corporation for Assigned Names and Numbers (ICANN) is responsible for the assignment of
IPv6 addresses. ICANN assigns a range of IP addresses to Regional Internet Registry (RIR) organizations.
The size of address range assigned to the RIR may vary but with a minimum prefix of /12 and belong to the
following range: 2000::/12 to 200F:FFFF:FFFF:FFFF::/64.
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