> call the result secure since anybody sharing your upstream L2 network, plus your ISP and anyone who can trick, force or coerce them into cooperating could still access your network
Ok, so the L2 thing isn't unheard of, but otherwise these are relatively unrealistic scenarios to be concerned about, don't you think?
I guess, but the fact remains that using RFC1918 is still both more effort and less secure than just using a firewall is, and that NAT doesn't help the situation.
Do you really want the security of your network to rely on your ISP always doing the right thing for you?
Ok, so the L2 thing isn't unheard of, but otherwise these are relatively unrealistic scenarios to be concerned about, don't you think?