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Community Member

Dropping an ISP

We are currently multihomed with three providers. We want to drop one of the providers, but seem to be unable to do so. I padded the routes out to the provider we wished to drop with our AS, and proper routing seemed to propagate. (with these guys not in most of the routes back to us). I shutdown the connection, and the routes fail to converge. As a matter of fact, a shorter route gets propagated anew from this AS, which is now unreachable. Could this be due to static routes being advertised from the ISP in question, even though I'm no longer connected to them? Censored and modified config attached. We wish to drop ChoiceOne, AS 13609


Re: Dropping an ISP


If you do not see this shorter path when you are peering with this provider, I would hazard a guess that the provider has static routes with high administrative distance pointing to you. When it no longer learns these routes via EBGP with your router, the floating static routes kick in and are redistributed into BGP.

The only way to really find out what they have done is to ask the provider, I suppose...



Re: Dropping an ISP


I think Paresh gave the right explanation. You can check this by looking at the originating AS for your 4 networks in case you shut the connection to 13609.

In case they are originating BGP updates on behalf of you, you should contact them and request a change of their behaviour.

This is causing a problem for you (even in case the line to 13609 goes down!) and they have to change their configs to avoid it.

Hope this helps


Community Member

Re: Dropping an ISP

Thanks Paresh, Martin, this was my thought also so I contacted the upstream... Actually discovered this because I wanted to test failover, and can't... The upstream made some unspecified change and actually made things worse. For two of my networks all protocols are slowed, traceroutes time out at a distance (usually 13-17 hops). And still I can't break their connection without being blackholed. This is Choice One (AS13609)... in the future my last choice...Wish me luck.

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