I don't know how much of it is ignorance, or resource constraints. I've worked with companies that have used disconnected AS's because they couldn't justify multiple AS's and they needed to multihome in multiple isolated locations. I've also worked with companies that deliberately de-aggregate prefixes due to link capacity issues. Network operators have to balance building an ideal network to what equipment, links, IPs and AS's they can justify. I personally rather see network operators de-aggregate and utilize space efficiently as opposed to hoarding larger prefixes to make their network appear like something it isn't. -Adam -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Ralph Doncaster Sent: Wednesday, November 13, 2002 11:46 AM To: nanog@merit.edu Subject: disconnected autonomous systems I've found there are many providers that have completely disconnected autonomous systems. For example Yipes (6517) uses L3 on the west coast and Williams on the east coast. 66.7.129.0/24 is advertised under their AS through WCG and 209.213.209.0/24 is advertised under their AS through L3. And the number of connected autonomous systems with de-aggregated prefixes appears to be even more common than a disconnected AS. It would seem that many (most?) network operators are just ignoring the more vocal opinions on NANOG. -Ralph