RFC1918 isn't big enough to cover all use cases. Think about a large internet service providers. If you have ten million customers, 10.0.0.0/8 would be enough to number modems, but what happens when you need to number video set top boxes and voice end points? I don't think anyone goes out and says "Lets go use someone else's space, because I don't want to use this perfectly good private space".
On Sun, Dec 17, 2017 at 3:42 PM, Richard <rgolod...@infratection.com> wrote: > > > On 12/17/2017 04:30 PM, Robert Webb wrote: > >> Will anyone comment on the practice of large enterprises using non >> RFC1918 IP space that other entities are assigned by ARIN for internal >> routing? >> >> Just curious as to how wide spread this might be. I just heard of this >> happening with a large ISP and never really thought about it until now. >> >> Robert >> >> >> It is more common than you would think. Why use public IP's when you > can have many rfc1918 options. Always amazes me after the initial confusion. > Richard >