Building a Mostly IPv6 Only Home Network

Don't use DCHPv6 at home. I tried: you will hate your life, lots of stuff doesn't support it. Android specifically has zero support for it, google says it never will.

Use SLAAC. It just works.

My ISPs change the /64 more often. So I use the ULA a lot more often. My router runs its own DNS server and then it advertises this DNS server using a ULA address.

Typically it's similar to ipv4, they try to assign the same address/prefix for the same MAC/DUID. The most common reason to lose your addresses is replacing your router. Hopefully new routers allow you to set the dhcpv6 DUID somehow...

I dunno, I've manually set up NAT (down to the sysctls and iptables) and it's... fine. There's a small learning curve, but it's small. You should of course run a firewall which NAT is not; that's also simple and just basic hygiene.

I do work with NAT, but the stuff I use does hole-punching pretty transparently. I run 2 VPSes to facilitate this. I don't use UPNP, I have it explicitly disabled everywhere (too much malware that tries to leverage it)

And yes I know that NAT has the same effect as a "deny all inbound" on IPv6. Which is something I would set there too if I did use IPv6 so I'd still have to do hole-punching anyway.

Thanks for sharing this! Every few years, i forget the "why" advantage of IPv6. :-)

I can think of at least two reasons why this isn't worth worrying about.

One is quantitative: you have to remember that 2^48 is a much much bigger number than 2^32. With 2^32 IPv4 addresses, you have about 0.5 addresses per human being on the planet, so right away you can tell that stringent allocation policies will be needed. On the other hand, with 2^48 /48 ranges, there are about 8,000 ranges per human being.

So even if you hand a few /48s out free to literally everyone who asks, the vast majority will still be unallocated. A /48 is only about 0.01% of what could be said to be a "fair" allocation. (And yet, a /48 is so huge in absolute terms that even the vast majority of organizations would never need more than one of them, let alone individuals.)

The other is that unlike, say, the crude oil we pump out of the ground, IP address ranges are a renewable resource. If you hand out a free /48 to every person at birth, then long before you start running out of ranges, people will start dying and you can just reclaim the addresses they were using.

/48s are "small" enough that we could give ~8 billion people each 35,000 of them and we'd still have ~1.5 trillion (over 300x the size of the ipv4 space) left over. Addresses are basically infinite, but routing table entries (which fragmentation necessitates) have a cost.

In IPv6 the smallest 'subnet' is /64 if I recall correctly.

It's weird having a subnet size equal to a complete IPv4 Internet worth of IPv6 Internets but I believe the rationale was that you would never in practise run of out IPs in your subnet. A lot of Enterprise IPv4 headaches are managing subnets that are not correctly sized (organic growth, etc.). IPv6 is always routable for the same reason (companies reusing RFC1918 making connecting networks a pain).

There are different headaches with IPv6 - such as re-IPing devices if they move subnet - i.e. move physical location, or during a failover etc.

I'm not sure what the best practise there is as many enterprises don't use IPv6 internally. In my experience anyway.

Yes. I wish they had simply used a more sane address length instead, and maybe given everyone 65535 addresses at most. More than enough for the craziest home lab ever.

Really, just adding 2 bytes to IPv4 would have fixed everything and made it a lot simpler to move over. IPv6 is overkill and I think that really hurt its adoption. I remember being at uni and being told "this is the next big thing". In 1993. And it's not even a big thing now. Not on the user side anyway, I can still access everything from IPv4.

/48 because ethernet mac addresses are that length and so you can assign everything that and find it.

If we actually get to the point of address shortages,

Either, NATv6 would become a thing, or instead I hope SLAAC would get deprecated and dhcpv6 would become mandatory so we could give out smaller than /64s

video games

Yes but these days overlay networks are a way more common practice for that, with their own benefits (overlay IPs are always encrypted)

That's only if you are behind CGNAT though. My fixed ISP doesn't use it.

IPv4 is pretty simple and good for LANs. Nothing wrong with sticking to it.

> your external IPv4 address rarely changes

Bad generalization. I'm sure policy about this differs a lot, but my consumer ISP definitely reassigns my home's v4 address periodically. I don't track it closely, but it seems that when my ONT power cycles more often than not it pulls a new v4 address.

Now, basing my privacy/security on this would be bad, but to GP's point, if I was using a static v6 block, not only would this address never change, each device in my LAN would have an extra identifier attached to it. External hosts wouldn't merely be able to identify "my house", but traffic from "my phone", "my kid's switch", and "my spouse's phone" would all have distinct addresses.

Of course, my ISP doesn't do v6 at all, so there's no dilemma :')