[arin-discuss] Trying to Understand IPV6

[Gary T. Giesen]

Using anything less than /64 for a subnet can be dangerous, especially
as a lot of devices are hard-coded to not accept any other subnet mask.

While I'd argue /64's should be used everywhere, there is some merit to
using /112's or similar on point-to-point links between routers, where
it's a known quantity what the devices support. In an environment where
you could have a large number of heterogeneous devices, you're asking
for a support headache to use anything else. 

/64's are the safe choice, and we're in no danger of running out of them
anytime soon (and probably not in my lifetime).

GG

On Mon, 2010-09-13 at 13:46 -0400, Scott Morris wrote:
> There really isn't a great repository for things, at least that I've
> seen...  But keep in mind that the binary works the same in IPv6 as it
> does in IPv4.  :)
> 
> So when you look at a /21, do you look at it as 2000'ish IPv4
> addresses?  (At which point a single /64 is more than enough)
> Or do you look at it as 8 x /24 networks (at which point a /61 is the
> technical equivalent)
> 
> /64 is used by many people as the de facto "network" addressing for
> any subnet because of all the magical EUI-64 addressing to work (e.g.
> less whiny customer calls = better).  But anyone doing DHCPv6 will
> quickly learn that a /64 is a SERIOUS amount of addresses than can be
> broken down internally to any variation they really feel like.  (/126
> = /30, etc.)
> 
> So to best answer that questions, you have to know a little about your
> customer and how they'll use the addresses.  /56 seems to be the way
> many folks are going with things, but that's 256 /64 networks or the
> veritable "boatload" of addresses that will be wasted beyond belief.
> 
> Remember in the old days everyone gave out IPv4 addresses like candy.
> Back then 4.2 billion addresses seemed like a lot...  Today, 340
> undecillion addresses seems like a lot... Times change though!
>  
> 
> 
> Scott Morris, CCIEx4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> 
> CCDE #2009::D, JNCIE-M #153, JNCIS-ER, CISSP, et al.
> 
> CCSI #21903, JNCI-M, JNCI-ER
> 
> swm at emanon.com
> 
> 
> Knowledge is power.
> 
> Power corrupts.
> 
> Study hard and be Eeeeviiiil......
> 
> 
> 
> On 9/13/10 1:24 PM, Schnell, Darryl wrote: 
> > Can anyone recommend a good IPV6 website for Beginners? I’ve read
> > about eight web sites which say the same things and I feel like my
> > head is going to explode. I guess the problem I’m having is trying
> > to understand how an IPv4 CIDR notation translates in an IPv6 CIDR
> > in order to fill out ARIN IPV6 Allocation Template future usage
> > section. My actual question is –
> > 
> >  
> > 
> > If I assigned a customer say an IPV4 /21 in IPV6 this would
> > translate into a /56? If I’m not mistaken a /56 would translate into
> > something like 65,000 host addresses? That just seems like a lot of
> > hosts to me, especially when most of the time I’m working with
> > networks that are /26 or smaller. I guess my big problem is
> > confusion over labeling. What would be the equivalent of
> > a /26, /27, /28 or have we done away with blocks that small and
> > simply would just assign a /56 instead?
> > 
> >  
> > 
> > Does any of the gibberish I wrote make any sense at all?
> > 
> >  
> > 
> > Any help anyone can offer is much appreciated.
> > 
> >  
> > 
> > D -
> > 
> >  
> > 
> > 
> > 
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