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Comment by mort96 | Hacker News Reader

That's a fair point. In my mind, residential ISPs give out public IP addresses and CGNAT is just for cell phones. But I recognize that the philosophy of, "we don't need to solve IP address exhaustion, we just need to keep people able to access Facebook" leads to CGNAT or multi level NAT.

Still, I do think that the solution of, "one IPv4 address per household + NAT" is a perfectly good system. I view the IPv6 mentality of giving each computer in the world a globally unique IPv6 address as a non-goal.

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Even if you go with one IPv4 per household + 1 per company you're going to be hard stretched to find room for that in 32 bits, at least after you add the routing infrastructure.

There are more households than IP addresses. They can't all have one each. So you need longer addresses, and then you're already reinventing IPv6.

There are roughly twice as many IPv4 addresses as households globally.

That's not enough.

For one, businesses and other entities also need Internet access. Cloud companies in particular needs a ton of addresses. That's gonna eat up a fair chunk of the remaining 50%.

Two, humanity is still growing, governments across the world are building new housing. That's gonna eat up another chunk.

Three, routing is hierarchical, and infrastructure organisations and ISPs are assigned blocks of addresses, not individual addresses. We can't just have a pool of free IP addresses and assign any address to any house in the world as needed. So even having 50% of IP addresses free wouldn't really be enough.

So in my mind, an IP addresses to household ratio of 0.5 means residential CGNAT is inevitable, even if we ignore legacy issues like individual universities and other institutions owning gigantic /8 or /16 ranges.

Regardless of the actual number, I'm pretty sure that IPv4 addresses are not proportionally assigned to each region according to # of households.

> That's a fair point. In my mind, residential ISPs give out public IP addresses and CGNAT is just for cell phones.

If you are giving out public IPs then you aren't really NAT'ing.

Hm? The ISP gives one IP address to a router in a house, that router uses NAT to let all the computers inside that house use the Internet through the one single shared public IP address. That's NAT, isn't it?

Well, in a strict sense, it is "you" who chooses to run a nat'ing router there, you could just have one single computer per ISP connection. Or have it run a proxy for you, or nat.

I mean, I understand that this feels normal today, that 10-20-50 devices need internet and that the way to manage that is to nat the connections, but your ISP isn't doing nat, it is you.

The model of "every Internet subscriber gets one IP address" only works thanks to NAT.

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