North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: IPv6 subnet calculators?

  • From: JAKO Andras
  • Date: Wed Feb 12 18:42:49 2003 
 Jeff,

> I am trying to find an IPv6 subnet calculator or even a "cheat sheet" that
> will help show how a /32 allocation is broken down into /40, /48 and /64

I guess that you don't even need a cheat sheet for that. All the prefix
lengths you mention are multiples of four, which means they're on nibble
boundaries. Since IPv6 addresses are usually written in hex, this is just
as simple as to break a dotted decimal IPv4 /8 to /16s or /24s.

Maybe the only common mistake you should be careful about: You must always
write down the digits to the next colon (16 bit boundary). So if you break
down 2005:2001::/32 into /40s, then the second /40 is 2005:2001:0100::/40.
(NOT 2005:2001:01::/40, because that would mean 2005:2001:0001::/40, which
is the 2005:2001::/40 prefix.)

Andras