Thank you Michelle

for obsoleting the only RFC which i manage to remember by number (apart from 1 obviously and 2705 and 2833 for "déformation professionnelle" - anyway all obsoleted aswell)

Sidenote: Why, could you ask, is it important to remember RFCs by its numbers? Valid Question. Let me explain: In an Industry where high regard is not based on individual technical skills or experience but on certifications acquired through mindless memorization it can be helpful to be able to do some RFC name and number dropping from time to time.

Back to the subject. RFC3330 has been obsoleted by RFC5735 (couldn't wait for 5777 heh?). Apart from cleaning out some mediaeval stuff (like the 14./8 and 24./8 blocks) there is an interesting addition of TEST-NET-1 to -3 blocks, described to be mainly for documentation purposes (RFC5737) they can also be confidently used in private networks.

Again, why? Could you ask. Whats wrong with RFC1918? Should be enough for any organisation, if not, better switch to v6. Good argument if you live in a well organised and documented environment.

But if you live with customers who tend to eloborate highly original solutions, tend to give a damn about documentation (mañana) and tend to look at public IP space from the same angle they look at software licenses or copyrights then you may encounter internal networks numbered 195.195.195.0/24 or 222.222.222.0/24 or 65.65.65.0/24 (all real examples).

Ask the Network Admin why if you dare:
- "We needed a network and couldn't remember what private networks we allready used but were sure that we did not use 195.195.195.0/24 anywhere."
- "Documentation?"
- "Who cares?"
- "But this is public ip space!"
- "Who cares? Anyways we live in an ALBA country. We just apply current 21st century socialism politics to networking. Las direcciones IP publicas ahora son de todos!. Socialismo o muerte! El pueblo unido jamas sera vencido!"
- "Tranqui, tranqui. Ok, ok, got it."

So under this circumstances RFC5735/5737 gives you a tool of temporary alleviation and somehow legal use of three most probably unused /24 networks (Most probably unused because it are sufficiently "random" numbers, would it bee something like 192.192.192.0/24 you couldn't be too sure). Naturally the goal should be to clean up and document the network ASAP to get rid of these again.

Now the only problem is to remember these numbers if i even can't remember the RFC's.

192.0.2.0/24 (TEST-NET-1)
198.51.100.0/24 (TEST-NET-2)
203.0.113.0/24 (TEST-NET-3)

Update:
Forgot to mention that if you need a bunch of temporary networks not overlapping with RFC1918 this is a nice one: 198.18.0.0/15 (RFC5735, RFC2544, Network Interconnect Device Benchmark Testing
), that should be enough.

RFC3330 - RFC5735 Comparison