### What binary digits are ipv6 addresses made up of

The ipv6 address is made up of 128 binary digits, which is four times the length of an IPv4 address, whereupon the IPv4 dotted decimal format is no longer applicable, and hexadecimal representation is used.

The advantage of IPv6 is that it greatly expands the space available for addresses, which are 128 bits long. If the surface of the Earth (both land and water) is covered with computers, IPv6’s 128-bit addresses are typically written in groups of eight, each in the form of four hexadecimal digits. For example: AD80:0000:0000:0000:ABAA:0000:00C2:0002 is a legitimate IPv6 address. This address is rather long and does not look or look easy to write. Zero compression can be used to reduce its length. If the values of several consecutive segments are all 0s, then these 0s can simply be expressed as::, and the above address can be written as AD80::ABAA:0000:00C2:0002. The important thing to note here is that you can only simplify the 0s of consecutive segments, and the 0s before and after them should be retained, for example, the last 0 of AD80 can’t be simplified. Also this can only be used once, in the above example of ABAA after the 0000 can not be simplified again. The purpose of this restriction is to be able to accurately restore the compressed 0, otherwise it would be impossible to determine how many 0s each :: represents.

### 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.