The NAT firewalls do not like P2P UDP traffic.
Majoritoy of the routers lack the smarts to passtrough QUIC correctly, they need to treat it the same as TCP essentially.
Example: Janky way to get return routing for traffic when you don't control enterprise routes.
Source: FW engineer
No doubt you think I should simply renumber all my VMs every time that happens, breaking internal connections. Or perhaps run a completely separate addrsssing in each vm in parallel and make sure each vm knows which connection to use. Perhaps the vms peer with my laptop and then the laptop decides what to push out which way via localprefs, as paths etc. that sounds so much simpler than a simple masquerade.
What happens when I want vm1 out of connection A, vm 3 out of connection B, vm 4-7 out of connection C. Then I want to change them quickly and easily. I’m balancing outbound and inbound rules, reaching for communities, and causing bgp dampening all over the place.
What when they aren’t VMs but instead physical devices. My $40 mifi is now processing the entire DFZ routing table?
What happens when I want a single physical device like a tv to contact one service via connection 1 and another via connection 2 but the device doesn’t support multiple routing tables or selection of that. What if it does support it but I just want to be able to shift my ssh sessions to a low latency higher loss link but keep my streaming ups on the high latency no loss link.
All this is trivial with nat. Now sure I can use NAT66, and do a 1:1 natting (no PAT here), but then I’m using nat and that breaks the ipv6 cult that believes translating network addresses is useless.
What do you have in mind.
And if 10.0.0.0/8 is not enough, there is always the old Class E, 240.0.0.0/4 - likely never going to be acceptable for use on the public Internet, but growing use as an additional private IPv4 address range - that gives you over 200 million more IPv4 addresses
How is it "less hassle"? You've got to use a second, fiddlier protocol and you've got to worry about collisions and translations. Why not just use normal IPv6 and normal addresses for your whole network, how is that more hassle?
> You can always support IPv6 at the perimeter for ingress/egress. If your cluster is so big it can’t fit in 10.0.0.0/8, maybe the right answer is multiple smaller clusters-your service mesh (e.g. istio) can route inter-cluster traffic just based on names, not IPs.
You can work around the problems, sure. But why not just avoid them in the first place?
Because, while less common than it used to be, software that has weird bugs with IPv6 is still a thing-especially if we are talking about internally developed software as opposed to just open source and major proprietary packages. And as long as IPv6 remains the minority in data centre environments, that’s likely to remain true - it is easy for bugs to linger (or even new ones to be introduced) when they are only triggered by a less popular configuration
My point was that NAT is for IPv4 address exhaustion.
There’s no point to using NAT for IPv6.
If your software doesn’t work with IPv6, and you need IPv4…that is subject to IP address exhaustion. So yeah you need NAT for IPv4.