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IPv6 solves the addressing problem, not the reachability problem. Good luck opening ports in the stateful IPv6 firewalls in the scenarios outlined in TFA: > An
by lxgr 9mo ago
IPv6 solves the addressing problem, not the reachability problem. Good luck opening ports in the stateful IPv6 firewalls in the scenarios outlined in TFA:
> And that assumes a single NAT. Many sites have a security firewall behind the ISP modem, or a cellular modem in front of it. Double or triple NAT means configuring port forwarding on two or three devices in series, any of which can be reset or replaced independently.
- 1970-01-01 9mo agoWith IPv6 you don’t forward ports at all. The device already has a public address.
- jlokier 9mo agoThat's the addressing problem, although I have some bad news on that: NAT is used with IPv6 in some places. The reachability problem is, even with public addresses, sometimes you have to do the same thing to "configure port forwarding" with stateful IPv6 firewalls as with double or triple NAT IPv4.
- lxgr 9mo agoThat's why I said "open ports", not "forward ports". Stateful firewalls are very much a thing on v6. Many mobile ISPs don't allow incoming connections by default, for example. Many CPEs (home routers) also come with a v6 firewall (I'd guess it's probably more common than not?), and not everybody has admin access to theirs.
- bandrami 9mo agoYou don't have to forward ports with IPv6 but you certainly can, and that means some remote sites you have to interact with will.
- bigstrat2003 9mo agoI'm not really seeing a reason why it would be impossible to open firewalls in that scenario. More work, sure, but by no means impossible. In any case TFA says right up front that it is trying to solve the problem of overlapping subnets, which IPv6 solves nicely.
- lxgr 9mo agoIt's completely impossible if you simply don't have the necessary access. Not everybody can administer all firewalls upstream from them. Nor can everyone control whether their connection supports v6, unfortunately.
- digiown 9mo agoHole punching is a thing. Ports are not normally completely blocked. They allow replies, which can be exploited to do make a connection. Obviously this requires an out of band signaling mechanism. Tailscale does this, so does WebRTC, iirc. See: https://tailscale.com/blog/how-nat-traversal-works https://tailscale.com/blog/how-nat-traversal-works
- lxgr 9mo agoYes, but I don't believe all firewalls support that, especially for TCP, and as you've mentioned, now you also need to maintain a handshaking mechanism. The complexity makes sense if you need to transport a lot of data peer-to-peer or the lowest possible latency, but if you don't, you might as well use that coordination server (which outbound-only clients are connecting to) for payload communication as well.
- direwolf20 9mo agoFirewalls don't track connections as carefully as you might think. They don't delete the mapping when an RST is received, so you can keep using it and receive a SYN in the other direction and now you have a connection.
- pcarroll 9mo agoHole punching actually works most of the time. A lot more often than you might think. But enterprise firewalls usually don't allow it. And some home routers fail when you check all the anti-intrusion options. But it's the same for other VPNs. In the residential and small-business space, it's pretty rare. You might need to point it out to the network guy. If the customer wants the service, they should be open to it.
- zamadatix 9mo agoThe article's proposed solution for IPv4 is a combination of VPN+NAT. The solution in IPv6 can be just VPN, sans NAT.
- bandrami 9mo agoIt can be sans NAT, but there's no guarantee it will be, and if a remote site chooses to NAT their IPV6 you still have to support it