Originally posted to the NANOG list. Relevant to PIER as a real-world example of what we have to solve.

On Wed, 3 Apr 1996, Paul A Vixie wrote:>

...

sooner or later we will have to kill off the /24's, which make up 70% of the routing table but offer way less than 10% of the total reachable destinations. perhaps now that address ownership has been put to bed, the gang of big providers can agree on a date after which they will all stop listening to or exporting any prefixes longer than /23? THAT would be the incentive the industry needs to look at private addressing and aggressive renumbering. who's willing to risk collusion lawsuits and lost customers? step right up and sign the register please.

Dalvenjah FoxFire <dalvenja@ict.org> replied,

I'm not sure if this is the most completely wrong place to ask this question, so please forgive me if it is, but I'm not sure where else to ask it...

You have legitimate concerns; I'm not sure that you'll like the answers.

As someone who's about to renumber a public school district from a /24 to something else, what would be the smallest network to get (from InterNIC) that would pretty much be guaranteed to be routed for the next few years? I'm thinking a /22 at the moment, but am not sure.

IMHO, I don't think you can guarantee that almost anything will stay routable, certainly anything less than an /18. Bluntly, there's no good way to guarantee routable prefixes. What is reasonable, while you are renumbering, to put in the hooks that make subsequent renumbering much less painful. PIER is ... ahem ... addressing these. Please share your major problems in renumbering with PIER. IMHO, the most important parts are making your end stations easier to renumber, using DHCP (or its predecessors) for end station IP addresses and DNS for server references. Obviously, there are other issues, but these are key. I can send you the draft router renumbering guide that has been posted to PIER but is not yet on the server.

Granted the best solution would be go to our provider (all the schools in Santa Clara County, CA go through the county office of education for internet access) and have them get an /18 or something and distribute that, but they don't seem to want that. Should I push them for this solution?

It certainly would be much cleaner, but I still don't think you are going to be able to guarantee you won't renumber in the moderate term. Growth curves are too steep.