IPv6, in a way, takes the concept of a MAC address and puts it on steroids. This became evident to me when I learned about EUI-64 addresses. And then my brain melted when I learned that any interface can be assigned an arbitrary number of unique addresses with varying purposes or contexts because the address space is truly *that big*.

When I consider that quality of IPv6’s design, it communicates to me an old and ideal vision of what we thought the internet would and should be - a hyper-connected, shared infrastructure where [Layer 3] identity is universally unique such that connectivity between any two arbitrary nodes is possible (which obviously isn’t true for NAT w/ overload).

I’m just a lowly SysAdmin who finally decided to get his CCNA - so I’m a nobody - but as I worked through the material I felt like I was paging through a history book or biography of how the Internet’s life came to be and all the mistakes made along the way. Most features felt like patches for design considerations that were overlooked. Examples: DHCP Snooping, STP’s various * Guards, and the mere fact that Layer 2 and Layer 3 addresses are distinct concepts.

I don’t think there’s any disagreement that NAT was co-opted as a security feature. I never hear that said in a positive way, either. I think if we were to start over, with IPv6 as the default assumption, the tools we’d develop for network security would look very different, but not at all impossible or any more difficult.

But again - I’m a nobody. Just thinking out loud here.

> the mere fact that Layer 2 and Layer 3 addresses are distinct concepts.

If it weren't you couldn't have the same IP over several interfaces.