What are the three representation formats for IPV6 addresses? And give examples?
There are three conventional formats that can be used to represent IPv6 addresses as text strings: the first is x:x:x:x:x:x:x:x:x, where “x” is a hexadecimal value that corresponds to each of the eight 16-bit segments of a 128-bit address. For example: 2001:fecd:ba23:cd1f:dcb1:1010:9234:4088 Some IPv6 addresses may contain a long string of zero bits. To facilitate textual description of such addresses, a special syntax has been developed. The use of “:::” indicates that there are multiple sets of 16 bits of zeros. “:::” can only occur once in an address and can be used to compress leading, trailing, or adjacent 16-bit zeros in an address. For example: fec0:1:0:0:0:0:0:0:1234 can be represented as fec0:1::1234 When dealing with mixed environments with IPv4 and IPv6 nodes, another form of IPv6 address can be used. That is, x:x:x:x:x:x:d.d.d.d, where “x” is the hexadecimal value of the 96-bit high-order byte of the IPv6 address, and “d” is the decimal value of the 32-bit low-order byte. In general, “IPv6 address mapped to IPv4” and “IPv4-compatible IPv6 address” can be expressed in this representation. These two types of addresses are discussed in later sections. For example: 0:0:0:0:0:0:0:10.1.2.3 and ::10.11.3.123.
ipv6 address format
The IPv6 address format is composed of 128 bits divided into eight 16-bit blocks. Each block is then converted to a 4-bit hexadecimal number separated by colons.
For example, the following represents an IPv6 address in binary format and divided into 8 16-bit blocks of 128 bits:
Each block is then converted to hexadecimal and symbolized by ‘:’:
Even when converted to hexadecimal format, the IPv6 address is still lengthy. ipv6 provides a number of rules to shorten the address. These rules are:
Rule 1: Discard leading zeros (ES):
In block 5, 0063, the two leading zeros can be omitted, as in (block 5):
Rule 2: If more than two blocks contain consecutive zeros, ignore all of them and replace them with a double colon ::sign, e.g. (blocks 6 and 7):
Consecutive blocks of zeros can be replaced with only one time ::so if there are still zeros in the block the address can also be a narrowed down to single zeros, e.g. (block 2):
IPv6 has three different types of unicast address formats. The second half of the address (the last 64 bits) is always used for the interface ID. the system’s MAC address is made up of 48 bits and is expressed in hexadecimal. the MAC address is considered uniquely assigned globally. The interface ID takes advantage of the uniqueness of this MAC address.
By using the IEEE’s Extensible Unique Identifier (EUI-64) format hosts can automatically configure their interface ID. first the host divides its own MAC address into two 24-bit halves. Then the 16-bit hexadecimal value 0xFFFE’s is clamped to those two halves of the MAC address, resulting in a 64-bit interface ID.
Global Unicast Addresses
This type of address is the equivalent of an IPv4 public address. In IPv6 global unicast addresses are globally recognized and uniquely addressed.
Global Routing Prefix: The most significant 48 bits are designated as the global routing prefix assigned to a particular autonomous system. The three most significant bits of the global routing prefix are always set to 001.
The auto-configured IPv6 address is known as the link-local address. This address always begins with FE80. The first 16 bits of the link-local address are always set to 1111111010000000 (FE80). The next 48 bits are set to 0. Thus:
Link-local addresses are used for communication between only IPv6 hosts on a link (broadcast service). These addresses are not routable so a router will always forward these addresses off the link.
Unique Local Addresses
This type of IPv6 address is although globally unique, but should be used in local communications. This address interface ID and the upper half is where the prefix, this status, global ID and subnet ID divides the lower half.
The prefix is always set to 1111110. the L-bit which is set to 1 if the address is locally assigned. So far, the L bit of 0 means undefined. Therefore, the only local IPv6 address is always from “FD”.
The range of link-local addresses is limited to this segment. Unique local addresses are local though global but not routed through the Internet, limiting their scope to the boundaries of an organization. Global unicast addresses are uniquely identified globally. They should enable addressing of the essence of the Internet v2.