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Can your run a looking glass script at home, and see what the BGP route is to a given IP via your cable/dsl provider?

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up vote 9 down vote accepted

Generally no.

The upstream(s) need to explicitly configure their routers to let you connect to them and receive their bgp feed.

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and assuming they have done that, how would the script than work? –  win08r2newbie Nov 8 '10 at 23:05
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The feed would constantly update the global routing information. Assuming you want to track a single IP, you would monitor said feed for changes relating to the netblock that IP is in. –  Joris Nov 9 '10 at 19:21
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You generally are not given access to your upstream ISP's routing table.

You can infer how they route with traceroute for a given destination IP. (keep in mind that this can change over time)

You could also write a script to login to other external looking glass systems to see how a particular route is being announced to the outside world. That might give you some insight too.

Route Views is one well known one. http://www.routeviews.org/

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I'm not sure you want a looking glass script. You could just traceroute out to the destination and see how it goes via the traceroute, and make guesses on the BGP path with the reverse DNS on the IPs... or you could use a looking glass that your ISP happens to have.

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