> That's not possible. IPv4 addresses are 32-bit numbers. Once you change that, you're no longer "preserving existing addresses". I am uniquely employee number

> That's not possible. IPv4 addresses are 32-bit numbers. Once you change that, you're no longer "preserving existing addresses". I am uniquely employee number 6100. That field is 32 bits in HR's database. If they make it 64-bit, I'm still 6100. > That's actually "once all routers and end devices are updated to support them". As the classic spamsolutions.txt says, "requires immediate total cooperation from everybody at once". No it doesn't, it requires gradual cooperation, as the 4.1-compatible hosts will still speak v4 as needed. Same as how v6 stack support was added even to hosts not using it. > It's more like "not needing NAT" than removing it; port mapping NAT is not a part of IPv4 (it's a hack on top of it), and it can be done identically in IPv6, but few do it on IPv6 since it's not necessary. Yeah but the goal is to remove it. The feature set of v6, including random addressing, is intended to support p2p applications. The authors of ipv6 did not envision NAT being enable by default. Defaults and intent matter more than technical details here. > IPv6 has done no such thing; the existing IPv4 blocks are still there. They aren't there on practically any ipv6 network, despite an optional ipv6 extension for v4-mapped addresses. That's the critical difference vs what I've described.