IPB210: IPv6-Mostly Is Really Dual-Stack

Ed Horley (0:10)

Well, welcome to the IPv6 Buzz, where we dare to dive into the 128-bit Azure space world. We're glad you joined us today, and we're going to be talking about IPv6 mostly.

Fact that it's really dual stack, but we won't really say that. I'm Ed Horley, I'm joined by my co-host Nick Buralia, Tom Caffeine. Say howdy, gents.

Tom Coffeen (0:30)

Howdy, howdy.

Ed Horley (0:33)

So let's dive into it. IPv6 mostly.

If you're listening to the show on a regular basis, you're probably hearing us talk about IPv6 mostly on the regular. So we won't cover that in too much detail. You can probably go jump to another show just to catch up on the details about that. But one of the things that skipped over often, and we just want to make sure that it's really clear for the audiences, IPv6 mostly has a whole set of dependencies about the fact that IPv4 exists on the network.

We could talk through the specifics about that, but we talk about IPv6 mostly like it's analogous to IPv6 only, because it's definitely a foothold or a way to get from your dual-stack network to a much more predominantly IPv6 run network. But the reality is that you still got v4 on there. And let's break that down and talk about why we have IPv4 there, and how this is useful, and maybe some of the thought process that went into making this a transition mechanism to allow networks that are dual-stacked to get over to predominantly IPv6 run networks. But it doesn't have to solely be IPv6. And so I guess that's the discussion point that we get into the details about. So maybe Nick, take us to the way back machine. Back in the dawn of time, when we had dual-stack only, and we were lucky if we got that to function. And then we were talking about trying to get to IPv6 only, and everyone's like, you're crazy, we're not shutting our IPv4 off. And we were stuck, right? We were basically stuck at that point.

Nick Buraglio (2:07)

Unmuted, sorry.

At that point, you were lucky to get dual-stack, right? It was the early days of the wagon train west to add that extra protocol on there. And when it was suggested, not that many years ago, that hey, we're going to start turning off IPv4, you'd get the, really? Well, that's ambitious kind of luck.

And they were right. There were a lot of things that didn't work, but lo and behold, IPv6 mostly appeared as sort of a, oh, this is going to, some people are going to hate this, and some people are going to be like, well, it kind of makes sense. I consider it the layer 2.5 of dual-stack, right? It's the MPLS layer of dual-stack because it's not quite IPv6-only, but it's further than just dual-stack on every host.

Ed Horley (3:12)

It's the ARP.

Nick Buraglio (3:14)

Yeah, I mean, it's the right in the middle, right? Because you have this network and your, and I've always, the analogy I've always used is that it lets your host system rise to the highest level of its network stack evolution, right? So if you can only do IPv4, that will work. If you can do dual-stack, that will also work. If you have a system that has all of the evolution completed, then it will do IPv6 only. And the network helps the host decide that through a couple of different ways. But it is in fact dual-stack.

Yeah.

Ed Horley (3:59)

And so we have some dependencies, and those dependencies rightfully make sense, given the fact that we're really running a dual-stack network. And I think the thing that's sort of unique about IPv6 mostly, and the reason the name is so apt, is that if you have a host that is incapable of doing IPv6 for any variety of reasons, it's an older device, it doesn't have a current network stack that supports Slack, whatever, and you don't have the capability to do any of the IPv6-related things on that interface for whatever reason, it will still get an IPv4 address via DHCP, it will still get a default route, it will get DNS, it will get all the things that a regular IPv4 network segment will get. And it will be happily chugging along doing its IPv4 thing on that particular VLAN that you set up in your network to run IPv6 mostly, or Wi-Fi, or whatever you have built for that device to come on.

And so the reality is that for devices that would struggle or be incapable of doing IPv4, they are perfectly, they're not a less than on the network, right? And I think that's an important point.