“Computer Networking: A Top down approach” by James Kurose.

I've 'learned' the OSI model / TCP/IP / DNS / etc - probably - more times than you in the last quarter century

It. Never. Sticks!

Subnets? ...yeah - I know they exist (and ... 'matter'?)

IP classification ranges? Same

IPv4 vs IPv6? Holy freaking crap! Those make ABSOLUTELY no sense to me!

I care about only 2 or 3 things:

- what [private] IP range(s) do we have on this network?

- what NAT rule(s) do I need to know to get from 'here' to 'there' (and back again)?

- is my publicly-facing device group accessible from the 'public' internet?

Nothing. Else. Matters.

(yeah, yeah, yeah ... all those CCxx network engineers are having heart palpitations right now - but I. Do. Not. Care!)

What is the problem?