Reply to post: Re: The internet will be privatised

We are absolutely, definitively, completely and utterly out of IPv4 addresses, warns RIPE

bombastic bob Silver badge

Re: The internet will be privatised

agreed. there is actually an IPv6/IPv4 gateway block that can be used to cover ALL IPv4 addresses with equivalent IPv6 ones. Why isn't THIS being used???

Sure, an IPv4-only system might have trouble routing back. For this you'd need a 'somewhat careful' NATing method, in effect the opposite of what IPv4 NAT already does, at whatever router is translating the IPv6 address space into an IPv4 one. It generally means "established connection" translations, to/from the IPv4 space, and it would really only work properly for services that aren't trying to connect out (but you would be able to connect TO them, and get responses back).

I expect this last part is the only real reason IPv4 needs to exist. but how ELSE could you map a bozillian possible IPv6 addresses down to a /32 address space?

So yeah, "said router" above would listen on the IPv6-mapped-to-IPv4 address. It would translate that incoming IPv6 packet into an IPv4 (assigning a private IPv4 to it) for the private network. The server on the private network would send traffic back, and the NAT on "said router" woudl translate it back to a public IPv6 to be transmitted the normal way. basically, "reverse NAT". And DNS for IPv6 could (in theory) be done the same way (as seen by the IPv4 side) for outbound connections, but you'd have to limit your "resolved" address space to 10/8 and 192.168/16 and so on, and expire the DNS records in a short enough time, and recycle the addresses 'as needed' to manage it.

[should be possible to "can" a solution to this with Linux or one of the BSDs, if it has not already been done]

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