NPM And standard page when not in access list

[2-MAdD]

How do i get an redirect to a standard page, when you try to open a page where the ip isnt in the access list?

My access list is RFC1918, and a few public ip's (11.12.13.14, 15.16.17.18 and 100.110.120.130).
But i want that all traffic that is coming from not the access list will be redirected to my home url.

So for example my home url is doma.in (which is open for everyone).
I created a proxy for important.data.doma.in which is only open for my access list (RFC1918 + a few public ip's).
So if IP 10.11.12.13 wants to see important.data.doma.in it should be redirected to doma.in (or show that page).

How do i do that in NPM?

Thanks for your answer