Addressing plan exercise for our IPv6 course

Brandon Butterworth brandon at
Sat Jul 24 11:40:35 CDT 2010

> > Enterprises of non-trivial size will likely use RFC4193 (and I
> > fear we will notice PRNG returning 0 very often) and then NAT it to
> > provider provided public IP addresses.

Eventually ARIN (or someone else will do it for them) may create a site
you can register your address and know that it really is unique
among participating registrants. Random is fine, unique is better.

Such a site would be the seed for when (if) we come up with the tech
for everyone to have PI and lose all the restrictions imposed so far.

> > I'm just hoping that we'll at least
> > see 1:1 NAT instead of NAPT being used.

I think that will be a common PI alternative. If people really don't
want NAT then we shouldn't provide reasons for it to exist.

RFC4193 seems to be the best enterprise plan. They can link to other
enterprises and change ISPs easily or multihome. They are not beholden
to any ISP or numbering authority. The global table doesn't explode.

> Why on earth would you do that? Why not just put the provider-assigned
> addresses on the interfaces along side the ULA addresses? Using ULA
> in that manner is horribly kludgy and utterly unnecessary.

Enterprises tend to want only one identifier to manage per device and
that it be unique and mostly permanent.

With several PA and ULA on each device, links to ISPs and other
enterprises, the combinations of addresses and paths to manage flows
and security over become too hard (if it's not simple it's probably not
secure). Every device becomes a router and firewall and the staff who
manage those aren't cheap.

> > This is to facilitate easy and cheap way to change provider. Getting PI
> > address is even harder now, as at least RIPE will verify that you are
> > multihomed, while many enterprises don't intent to be, they just need low
> > cost ability to change operator.
> > 
> Why is that easier/cheaper than changing your RAs to the new provider and
> letting the old provider addresses time out?

And changing all the ACLs based on the old providers addresses

And allowing for all the 5 - 15 year old kit that predates this and
won't be upgraded (we have that problem with NT embedded in systems
with 10year+ refresh cycle)


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