It's been a few years but I've yet to see a consumer grade router that lets you mess with IPv6 firewall rules. I don't even know what these routers use for a default policy.
They all seem to have web ui's for IPv4 firewalls and port forwarding though...
You can have dynamic prefix that can change with every moment on your wan interface, but then you have static IPv6 rules and you cannot specify something like use current prefix there.
So I understand if the first reaction is screw that.
If my internal network is 10.0.0.0/8 and I have 100,000 hosts and a single IPV4 address that they all appear to be to the public Internet, I’ll sleep a lot better than if I had all 100,000 hosts with public routable IPV6 IP addresses attached to them.
Yes, you can depend on a firewall to protect you but at the very least it exposes information about your internal network and at worst opens you up to future firewall flaws.
I remember the days when people used to have every system have it’s own public IP address. People would scan for broadcast addresses of their networks and we got Smurf attacks as a result. Obviously those wouldn’t work with properly firewalled hosts but it still scares me.
All routers w/ firewalls will/should have them.
While I get that firewalls are probably safe like 99.99% of the time… I’ve gotta say, I just don’t trust software to not have vulns of some sort that someone important already knows how to break. So eg for a corporate network I would be hesitant to do this, for my personal network not so much (unlikely that a 3 letter agency gives a shit about what I do).
Additionally. Firewall changes can sometimes fail for whatever reasons so you might have accidentally exposed a node publicly for some time.
Making those nodes not reachable from the internet seems prudent. It’s like your office building has a public address but your office assignments don’t need to be public.
For the whole world there is absolutely no difference betwen routable address, non-routable address or even an absense of the machine... behind a firewall with drop all on a public interface.
You are correct in theory. What you don’t seem to be taking into consideration are firewall vulnerabilities or other unknown things that could happen that make it different from a practical standpoint.
I started an ISP from the ground in 1996. I’ve seen a lot of weird stuff. You seem to just hand waive it away like firewalls are this perfect bastion of security.
Maybe you have more experience than I do?
IPv6 with a /64 routes one of 18,889,465,931,478,580,854,783 possible IP prefixes to your router. Everything that happens behind that is opaque. There are so many IPs in that prefix that people can't even guess which ones you're using. It's easier to guess internal IPv4 NAT addresses.
The internet can't see your IPs. "Publicly routable" doesn't mean much when you're talking about prefixes.
And anyways, when you have a NAT you're probably routing traffic through a level 4 balancer or jumphost or using a VPN somewhere in your LAN.
You can also just start in the middle of a block and make a sequence of 10,000 IPs effectively unguessable.
I don't buy that keeping addresses private has much value, but IPv6 still isn't worse than NAT in that respect.
SLAAC
Pretty weird. For internal stuff I would be using IP addresses to identify peers. Ephemeral IP addresses in logs aren't very useful.
Rather than constantly update them as our servers change, we route through a NAT. I wouldn’t know how to do it with IPv6. Maybe the service provider could safelist a subnet?
Yes, thats what prefixes are for. Although its unpractical in IPv4 world, in IPv6 it is the way to whitelist a range of ips.
Exposing your LAN confguration for the world to see is insanity, it's like hiding your private SSH keys in a password-protected Excel file.
And yes, you need both NAT and firewall. They're complimentary technologies and do not replace each other.