On Wed, 29 Aug 2001, Clayton Fiske wrote:
the /24s of small multihomers is half the routing table (see geoff's data)
This can't possibly be correct. The last figure I read was that there are about 70k /24s. There are about 21k AS numbers out there. This means that by far most of the announcements, including /24s, are the result of lack of CIDR. Either because ISPs have a relatively large number of PA blocks (address conservation) or because of lack of aggregation.
Small multihomer /24s aren't necessarily their own. I've dealt with plenty of customers multihoming with a /24 from their other provider without running BGP. No extra AS number, but the /24 still shows up in the global table. Also seen customers with their own /24, but having us originate it rather than doing BGP with them.
I've never dealt with a customer with such a setup, but with at least a dozen BGP multihomers. I'm sure that people are multihoming this way, but I'm not so sure these BGP-less multihomers make up half the routing table. I've tried to gather some statistics. They aren't very good, but what I got was 1209 "inconsitent paths" below 212.x.x.x. Apart from the people who don't aggregate the high number or /24s in the global routing table is probably also to a large extent due to people not wanting to renumber and taking addresses with them to another ISP.