Using IPv6 with prefixes shorter than a /64 on a LAN

Sat Feb 5 00:45:17 UTC 2011

In message <4D4C8AF8.1030703 at brightok.net>, Jack Bates writes:
> On 2/4/2011 5:11 PM, Mark Andrews wrote:
> > No, a /48 is equivalent to a single IP.
> >
> > You loose a little bit with small ISPs as their minimum is a /32
> > and supports up to 64000 customers.  The bigger ISPs don't get to
> > waste addresses space.  And if a small ISP is getting space from
> > a big ISP it also needs to maintain good usage ratios.
> >
> 
> Read the rest of what I said again. In the layout I used, a /32 is a 
> /32. a /28 is a /28. Yet when you look at what is being assigned in IPv6 
> and you look at what we assign in IPv4, it's pretty laughable.
> 
> It took years for me to get to a /16 of IPv4; where a /16 of IPv4 is 
> small change for many large providers. In IPv6, a /16 is well out of my 
> league and much larger than many large providers will ever need.

A /16 of IPv4 is a /32 of IPv6 if you were only delivering 1 address
per customer.  If you were delivering /28's to customers that /16 is
equivalent to a /36.

/32 get assigned to ISPs.  Those ISPs assign /48s downstream.  The
only place where that doesn't happen is ISP to ISP assignments
(resellers).

/48 get assigned to everybody else.

The whole internet has shifted a minimum of 16 bits to the right.
In many cases it will be 32 bits to the right.  If ISP's only give
out /56 then the shift is 24 bits.

I used to work for CSIRO.  Their /16's which were got back in the
late 80's will now be /48's.

Mark

> >> A /28 (medium ISP) is equiv to an IPv4 /28. A /24 (high
> >> medium, large ISP) is equiv to an IPv4 /24. A /16 (a huge ISP) is equiv
> >> to an IPv4 /16. Get the picture?
> >>
> >> So, I currently route a /16 worth of deaggregated IPv4 address space
> >> (sorry, allocation policy fault, not mine). There is NEVER a time that I
> >> will be allocated an IPv6 /16 from ARIN. Heck, the most I'll ever hope
> >> for is the current proposal's nibble boundary which might get me to a
> >> /24. I'll never talk to ARIN again after that.
> >>
> >>
> >> Jack
> >>
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org