I have been compressing IPv6 addresses but for some reason I can't compress this one:
2b06:0000:0000:1f2b:d77f:0000:0000:89ce
This is what I compressed it too: 2b06::1f2b:d77f::89ce
But this is not working, and I wonder, why.
This is the correct way to do it: 2b06::1f2b:d77f:0:0:89ce
You can't have :: more than once in one address.
This 2b06::1f2b:d77f::89ce would be ambiguous, as it could expand to
2b06:0000:1f2b:d77f:0000:0000:0000:89ce,
2b06:0000:0000:1f2b:d77f:0000:0000:89ce, or
2b06:0000:0000:0000:1f2b:d77f:0000:89ce.
The Standards Track RFC 5952, A Recommendation for IPv6 Address Text Representation explains:
4.2.3. Choice in Placement of "::"
When there is an alternative choice in the placement of a "::", the longest run of consecutive 16-bit 0 fields MUST be shortened (i.e., the sequence with three consecutive zero fields is shortened in 2001:0:0:1:0:0:0:1). When the length of the consecutive 16-bit 0 fields are equal (i.e., 2001:db8:0:0:1:0:0:1), the first sequence of zero bits MUST be shortened. For example, 2001:db8::1:0:0:1 is correct representation.
You can have more than :: in one address
the correct answer is 2b06::1f2b:d77f:0:0:89ce
