In a message written on Thu, Aug 15, 2002 at 11:41:17PM -0400, Richard A Steenbergen wrote:
IMHO, using only prefix limits on a customer is actually doing them (and the rest of the internet that listens to your announcements) a disservice.
I think you might be missing a highly useful case of using max-prefix with customers. Many customers will want to deaggregate their blocks, and/or leak more specifics. While I don't want to argue if that is good or not, the end result is most ISP's allow this in some form. Consider the difference between: Case 1: a.b.0.0/16 exact match prefix filter Customer calls in, asks for change. a.b.0.0/17 + a.b.128.0/17 exact match prefix filter. Case 2: a.b.0.0/16 le 19, max prefix 6 The second case allows customers to make changes with no delays, and reduces the amount of work for the ISP. It still enforces some level of aggregation automatically to protect the system, but also gives the customer some flexability. Generally I'd recomend something around twice the number of prefixes, with some sort of floor. So, if you registered 200 prefixes, you could announce 400 routes from them, with a maximum length as set by your ISP. -- Leo Bicknell - bicknell@ufp.org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/ Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org