Private internets

Posted on May 23, 2023

I’m not a networking person. I can to grasp the most critical parts on a conceptual level, and I’m able to copy and paste a CIDR block in some Terraform code, but it’s not an area I’ve worked a lot in.

But, as a part of studying, I needed to refresh some foundational knowledge. And suddenly I found myself reading RFC 1918 Address Allocation for Private Internets with my morning coffee. Just the title is intriguing on its own, I wish we talked more about internets in plural. Maybe that terminology is on its way back?

Older internet documents tend to have a nice tone to it:

The Internet has grown beyond anyone’s expectations. Sustained exponential growth continues to introduce new challenges.

And in section 3 the private address space is defined:

The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets:

 10.0.0.0        -   10.255.255.255  (10/8 prefix)
 172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
 192.168.0.0     -   192.168.255.255 (192.168/16 prefix)