How does Linux NAT a ping?

The other week I moved my ISP. The AS my house belonged to obviously changed to the new ISP, and I got a new v4 IP

All I had to do was update my Wan router to forward trafffic from the new Ip.

Instead with ipv6 I would have to change every node on my network, update my internal DNS.

Now in theory I could have my own /48 which I take with me. That relies on my new ISP being willing to advertise it (which my current one does) but it’s not particularly common.

However a week ago my phone line was cut. I got a 5g mifi out and moved my wan connectivity through that until the cable was fixed. Again a nice simple masquerade on that interface and all was good (well not that good - very poor signal where I live)

But the elephant in the room is of course all that ipv6 stuff aside, I still need to run a dual stack (or use trashy nat abstractions). It increases my work for no benefit.

But taking about work, how about there?

I have a fleet of vehicles on internal 172.16/12 subnets, they plug together and route to each other, and route from where they are via a variety of vpn connectivity (hoping that at least one method will work, as there’s rarely a signal in the basements these park)

If I moved them to ipv6 then again I’m back to having to move my /48s. Except these vehicles get internet from various sporting venues - most of which struggle to turn off MITM/443 or unblock UDP, that’s just not going to work in a world where they turn up at 10am Saturday morning and need to be working 2 hours later.

What business benefit is there for me to double the workload and double the risk by moving to dual stack?

https://datatracker.ietf.org/doc/draft-mishra-6man-variable-...

> We have to deal with the world we live in, not the world we’d like.

No we don't. Some choose to just put up with shittiness, others enact change.

IPv6 with assigning end users a whole /64 and end-devices continually churning through privacy addresses is a start. But even then some form of NAT is still required to nimbly use source prefixes from different horizon providers - eg to avoid spilling your geographic location or opening yourself up to low-effort legal shakedowns.

An example: on my local network I've got an everyday web browsing VM and a torrent VM. They each have static 192.168.x.x addresses, both so I can ssh in for administration and also to control their view of network services. They each see a completely different Internet horizon through the router - the web browsing goes out from a rotating datacenter IP, and the torrent one goes out from a consumer VPN. Each of those outgoing horizons uses NAT - any of my hosts using that rotating data center IP appears the same, and any of my host using the consumer VPN appears the same as every other customer using that same VPN node.

What is the no-NAT equivalent of this? Make that rotating data center IP and VPN external IP into subnet allocations, somehow feed that addressing information back to the hosts that are using it, and dual-home each VM with two routable addresses? For equivalent mixing on the consumer VPN there would also need to be some ARP-like protocol that let me continually rotate the address.