Ipv6 help

Thu Aug 27 08:12:56 UTC 2020

On 27/Aug/20 09:33, Brian Johnson wrote:

> If an ISP provides dual-stack to the customer, then the customer only uses IPv4 when required and then will only use NAT444 to compensate for a lack of IPv4 address space when an IPv4 connection is required. What am I missing?

While modern OS's prefer IPv6, it doesn't mean the end-service supports
IPv6 yet. If the end-service only supports IPv4, the OS won't try to
connect on IPv6.

More importantly, a customer assigned a public IPv4 address will never
need to use the ISP's CGN nodes. NAT44(4) will only be required for
customers that are unfortunate enough to require connectivity at a time
when the ISP can no longer provide a public IPv4 address to them.

You can't dynamically cycle customers between public and private IPv4
addresses based on demand. It's either they have a public IPv4 address,
or a private IPv4 address. Not both. Yes, there are way you can do this,
but it's not worth anyone's time and headache.

464XLAT means customers can only live on IPv6. The ISP can put aside a
small amount of IPv4 to bridge connectivity between an IPv6-only
customer to an IPv4-only service for as long as that end-service is
IPv4-only. Once that IPv4-only services wakes up, gets some clue and
turns on IPv6 (Sony and PSN, that means you), that is one online
resources less that the IPv6-only customers requires the 464XLAT
translation to reach.

As more end-services turn on IPv6, there is nothing the ISP needs to do
on the customer side, as they are already on IPv6, which was the biggest
advantage of the NAT64/DNS64 transition mechanism, and is the biggest
advantage of 464XLAT.

Thus, the ISP's demand for 464XLAT reduces (and eventually goes away),
as does their need to retain whatever amount of IPv4 space they required
to support the 464XLAT nodes.

Transitions mechanisms that seek to maintain IPv4 at the customer side
expose themselves to additional migration work when the majority of the
world is on IPv6. This is why I generally recommend ISP's (with the
exception of my competitors, of course) to focus on 464XLAT, as when we
get to that point, nothing needs to be done with the customer. There is
value in that!

Mark.