2.2. Zero Compression

2.2. Zero Compression

'A special syntax is available to compress the zeros. The use of "::" indicates one or more groups of 16 bits of zeros.'

It is possible to select whether or not to omit just one 16-bit 0 field.

2001:db8:aaaa:bbbb:cccc:dddd::1

2001:db8:aaaa:bbbb:cccc:dddd:0:1

In cases where there is more than one field of only zeros, there is a choice of how many fields can be shortened.

2001:db8:0:0:0::1

2001:db8:0:0::1

2001:db8:0::1

2001:db8::1

In addition, Section 2.2 of [RFC4291] notes,

'The "::" can only appear once in an address.'

This gives a choice on where in a single address to compress the zero.

2001:db8::aaaa:0:0:1

2001:db8:0:0:aaaa::1