disconnected autonomous systems

Stephen J. Wilcox steve at telecomplete.co.uk
Wed Nov 13 21:12:08 UTC 2002

On Wed, 13 Nov 2002, Daniel Golding wrote:

> I suppose that depends on how many static routes you would need, and how
> many routers you would have to touch.
> If you have 10 sites like this, and add or remove several blocks every day
> (an extreme, of course), then you could end up manipulating many statics
> on numerous routers, which, aside from being a waste of engineer time, can
> lead to fat-finger mistakes.

this is a hack whichever way you look at it.. just that its better than a
default and acheives a result more like the contigous AS would have had than an
end user network.. hmm i wonder if this would work if you ibgp peer your
discontigous border routers and use a route-map to make sure the routes point at
your upsteam - would remove the statics and your manual engineering issues. 

argh what am i saying.. now i'm promoting this setup!

> Since when did default routing become bad form, on a transit-buying
> network?

if you are a proper ISP with a full routing table you dont need a default and
having one merely sends junk to your upstream, i guess thats chargeable so maybe
they think its a good thing but it doesnt really fit with the various nanog
threads on tidying up bogon packets as they hop around the net.


> - Daniel Golding
> On Wed, 13 Nov 2002, Stephen J. Wilcox wrote:
> > > 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
> >
> >

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