As I sat in the auditorium listening to the speakers at the NANOG meeting Thursday and Friday, a realization came to me. Almost every speaker there who happened to talk about the problems with space and CIDR and what-not said "renumbering is a fact of life", or "renumbering is a simple method to solving these problems". While contemplating this, I realized that every speaker who said something along these lines really hasn't done massive renumbering to fulfill CIDR plans--they either have this HUGE block (i.e., major provider like SprintLink) that just needs to be aggregated on out-bound or aren't involved in the direct operation of NSP/ISP's. I've seen a specialty provider renumber about 15 class C's _twice_, the first because he changed providers and they urged him to CIDRize. He then had to change again when the first provider didn't live up to the contractual obligations. Because of a lack of planning on his part, he lost 20% of his customer space during/after these renumberings--customers don't want to put up with problems such as a) applications which compute the IP address into an equation with the license number, b) problems with _all_ parameters not being changed in terminal servers and hosts, c) DNS problems with off-site backup servers, and a few others that just generally made his customers not happy. (Keep in mind that "a)" above generally requires you to purchase new licenses from the software manufacturer.) The problem, you ask? I don't see very many resources available which help ISP's to renumber more easily--time line planners, reminder lists with commonly-missed parameters, etc. I realize that renumbering is a fact of life--my last post, however, shows my true feelings regarding most pre-CIDR blocks; that their providers should be willing to allow customers to keep using the space they allocated in the pre-CIDR days. If there are these renumbering resources available, make sure that the small and big providers alike are making them available to the customers who are willing to attempt a re-number. Make sure the customer service of the provider is willing to deal with the complexities of renumbering (and keep in mind it _IS_ a very complex project--EVERYTHING from IP addresses to static routes to applications which are hard-coded). Unfortunately, the ISP that I saw change providers didn't have this help at their fingertips--they could have potentially saved almost all of the customers they lost. My thanks go out to everyone who made this NANOG one of the best--keep up the good work! /cah