We know that IPv4 addresses are mostly represented in a dotted decimal form like 192.168.10.1, and if written with a prefix mask then it would be written like 192.168.10.1/24, where /24 is the network mask.

But IPv6 is long addressing format. IPv6 is 128 bit long and usually represented in hexadecimal format of addressing. IPv6 representation includes 8 sets of four hex digits separated by a colon(:).

For example:

`fffe:3465:efab:23fe:2235:6565:aaab:0001 `

Note:-
Mostly each set of four digits is termed as “Quartet”, however the term Quartet is not official.

IPv6 addresses are represented in two forms:

1. Unabbreviated –
E.g.:

`fe00:0000:0000:0001:0000:0000:0000:0092 `
2. Abbreviated –
E.g.:

`fe00:0:0:1::92 `

Rules to Abbreviate an IPv6 Address:

1. In each quartet, remove the starting & consecutive 0s (0001 -> 1, 0000 -> 0 & 0092 -> 92).
2. If there are two or more consecutive quartet of all 0s, replace it with double colon (::), but you can use double colon only once in a single address.

But in the above example, two or more quartet of all 0s occured two times, then which quartet to be replaced? In such cases, the highest no of consecutive 0s are replaced by a double colon(::). Examples:

```◙ 1111:2222:3333:0000:0000:1000:ffee:0001
It can be written in abbreviated form as 1111:2222:3333::1000:ffee:1

◙ 0001:0002:0003:0000:0000:1023:0000:0022  -> 1:2:3::1023:0:22

◙ ffee:0000:0000:0001:0000:0000:0000:0001 -> ffee:0:0:1::1

◙ 1a2b:0000:0000:0000:0000:0000:0000:0002 -> 1a2b::2 ```

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