Companies using public IP space owned by others for internal routing

Tom Carter m1enrage at
Sun Dec 17 22:48:49 CST 2017

RFC1918 isn't big enough to cover all use cases. Think about a large
internet service providers. If you have ten million customers,
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 <rgolodner at> 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

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