Simplifications
The full representation of eight-4-digit groups can be simplified by several techniques, eliminating parts of the representation.
Leading zeroes
Leading zeroes in a group can be omitted, but each group must contain at least one hexadecimal digit. The previous example address can be simplified as:
2001:db8:85a3:0:0:8a2e:370:7334
Note the removal of two sets of leading zeros and two sets of octets that are composed of zeros.
Groups of zeroes
One or more consecutive groups of zero values
can be replaced with a single empty group by using two consecutive
colons (::).
- Substitution can only be applied once in an address, as multiple occurrences create an ambiguous representation.
- If more than one such substitution canbe applied, the substitution that replaces the most groups must be used. If the number of groups is equal, then the leftmost substitution must be used.
With these rules, the example address is further simplified:
2001:db8:85a3::8a2e:370:7334