[tsaoutourpants]

> But we're at the point in some place where there aren't even enough IPv4 addresses to give to ISP customers even if they're using NAT.

Er, that's a slight exaggeration. It's not uncommon to have 2,000 or more NAT clients behind a single public IP address. 2K * 4B = 8 trillion possible hosts... about 1,000 hosts per living person.

[kaliszad]

Well, it has limits. You can hide 2000 people behind an address but they might have sporadic connection issues, long held connections such as SSH sessions will be very annoying to support [0] or the users will have to resort to frequent keepalives to make it work regardless, which produces more traffic to destinations you probably don't have in a cache. In some jurisdictions you have to log which customer used what IP (and port) at which point. You can do static assignments but you will have customers (customer homes, e.g. family with perhaps 10 devices or so could be realistic) for which 1000 ports just will not be enough do you will have to dynamically assign spare ports and log those. You might also get more support calls, because the NAT is dropping connections to radically in a peak e.g. a soccer match or whatever. Also the CG-NAT gateway isn't for free and the bigger it needs to be, the pricier it is. Also you might still need to buy some IPv4, perhaps more than you would need to buy if you deployed IPv6 and used it for the connections, where it is possible, taking e.g. almost the full load to Google/ YouTube and Facebook off your gateway.

[0] https://anderstrier.dk/2021/01/11/my-isp-is-killing-my-idle-...