fe80 IPv6 Link Local prefix is 10 bits?

michael salyers

I'm confused as to how the fe80 prefix is 10 bits and not 16.

Ronnie Wong

@michael-salyers,
The notation you see is standardized so you understand that the significant bits are the 1st 10 bits of 128 bits.
Convert FE80:: to Binary...
Binary:
*1111.1110.01*00.0000::

What you see is = 16bits but the /10 means that only the first 10 bits will remain unchanged...(i.e. FE8..). So the range in HEX is the following:

FE80:0000:0000:0000:0000:0000:0000:0000
through
FE8F:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF

note that the first 10 bits remain unchanged as the last 118 bits do. So `FE80/8 has a range of (2^118) addresses = ~33,230,700,000,000,000,000,000,000,000,000,000,000,000

michael salyers

Thanks for the thorough explanation