I am testing the creation of an enforced default route of only public IPv4 space via OpenVPN. OpenVPN does not support
'iroute 0.0.0.0 0.0.0.0'out of the box, because it contains code that rejects it. But if you remove that code and get iroute 0.0.0.0 to work, logically the connection times out after a while because OpenVPN gets confused.
I found out that the minimal range to iroute is a /4. So if you want to divide all IPv4 space into /4 blocks, you end up with 16 blocks ranging from 0.0.0.0 to 255.255.255.255. But this contains all routable and unroutable IPs... so the list needs to be further delimited.
Because of a non-generic setup I cannot use redirect-gateway stuff. That's why I I am looking for a list of subnets, that is as short as possible, of the public IP ranges that exist. The list has to exclude ranges that are reserved (and my own server's public IP/32). Basically, I'd like to have a list of the opposite of RFC 5735 (page 6)
Does such a list exist and/or how can one be generated?