Why do we still need IPv4 when we are migrating to IPv6...

Tore Anderson tore at fud.no
Thu Feb 12 12:24:50 CET 2015

* Anfinsen, Ragnar

> I am working with my management team to implement IPv6, but I got an 
> interesting question from one of the managers; Why do we need more
> IPv4 if we are moving towards IPv6?

IPv6 doesn't relieve you of IPv4 growth pains until you can start
shutting down IPv4 in parts of your network, and reassign those
reclaimed IPv4 addresses to more valuable end-points (such as the CPEs).

However, once you have implemented IPv6 (and I understand that your new
network architecture supports native IPv6?), you can actually do stuff
like that. Mikael already mentioned MAP and lw4o6, and I'd just like to
add that this does not necessarily mean oversubscription of IPv4
addresses - at least with MAP, you can still assign "whole" /32s to
customers (or even larger prefixes for that matter).

These technologies also allow for more efficient utilisation of your
available IPv4 address space then what you're usually able to
accomplish in a traditional IPv4 network. If you assign a /24 to the
MAP service, you can make use of every single one of the 256 IP
addresses - including the .0 and .255 if you so desire.

You can do similar stuff in the data centre BTW, and I'm sure my
employer would be happy to have me help you out with that. ;-)

> A quick background; We are having discussions around IPv4 and IPv6
> and the need to eventually buy more IPv4 addresses to keep a premium
> level on our Internet access.

Can you really with a straight face today call your product «premium»,
when it lacks the IPv6 support at least two of your largest competitors

If you consider the existence of optional/opt-in IPv6 support as
sufficient to call the entire product «premium», then perhaps you could
extend that line of reasoning to public IPv4?

In other words, give your customers to shared IPv4 by default, but allow
them to opt-in to get a public IPv4 address. Some percentage of your
customers won't care to do so as they're perfectly happy without (just
as they might be perfectly happy without IPv6), leaving you with
available IPv4 addresses you can assign to your CGN/MAP/lw4o6/whatever
equipment and to those of your customers who opt in to get public IPv4.


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