disconnected autonomous systems

Stephen J. Wilcox steve at telecomplete.co.uk
Wed Nov 13 20:46:07 UTC 2002

> Of course, it required you to point default routes out your upstreams, as
> you will not see the prefixes from one discontiguous island, in another,
> thanks to BGP loop detection.

ouch. bad practice defaulting like that, however to static route your individual
blocks wouldnt be a problem

> Several large access ISPs have run in the fashion for extended periods.

whats the opposite of autonomous? dependent? so AS becomes DS? :)

seriously tho, if an AS ceases to be autonomous then theres little point in
having them and you may as well do global routing on prefixes with a hop count
hmm can RIP handle 120000 routes? 

> As far as aggregation - they are a couple reasons to not aggregate, but
> the vast majority of it is sloth.

like to meet C&W peering policy etc? the only valid reasons imho are traffic
engineering and customer multihoming

> Finally, in regard to "vocal opinions on NANOG" - well, anyone who has
> read NANOG for a while knows that vocal isn't always correct.

altho it gives an indication of best practice and therefore policy and like the
other thread on filtering RIR allocation boundaries, sure you can go and do your
own thing but dont complain when providers start filtering your routes and
ignoring your prefixes!


> - Daniel Golding
> On Wed, 13 Nov 2002, Ralph Doncaster wrote:
> >
> > 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.
> > is advertised under their AS through WCG and
> > 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
> >
> >
> >

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