Determine difference between 2 BGP feeds

Bill Nash billn at odyssey.billn.net
Tue Apr 18 22:08:41 UTC 2006



On Tue, 18 Apr 2006, David Andersen wrote:

> Much of what Bill described below is already present using Nick Feamster's 
> bgptools release:  http://nms.lcs.mit.edu/software/bgp/bgptools/
>
> Start with zebra / quagga / etc., which do a great job of dumping tables and 
> updates.
>
> Then use bgptools to take the MRT-formatted dumps that Zebra spits out and 
> turn them into text, etc.  With the '-q' option, can insert the BGP updates 
> or table snapshot directly into a SQL database.

My peer actually comes from a Zebra box, so I'm not talking directly to 
any production devices, in the event that I want to bounce my db feed up 
and down (debugging, featuritis treatments, etc) Z/Q + bgptools is a great 
suggestion for doing complex reporting/comparison on the routing tables, 
though. I've got a need for a more real-time view, so my setup fits me a 
little better than your suggestion, but potato/potatoe. =)

> then the libbgpdump.a library gives you lots of cool things on top of that. 
> You'd have to do a little work to get the analysis tool you want, but it's 
> pretty easy.  Use the 'buildtree' starting program to build the prefix tree 
> from each provider and then compare those two trees (see which prefixes are 
> present/not present, see if any parts of the IP space are unreachable in in 
> one and unreachable in the other, etc.)

This is pretty interesting, I'll have to tinker with it, especially since 
I know one of my providers doesn't give me a full routing table.

> It starts as Bill suggested - a read-only BGP peer from the devices, which 
> takes about 3 seconds to set up.

And for folks to whom this is new stuff: don't be an idiot, put 
Zebra/Quagga up as a peer/buffer for attaching analysis tools to your 
network. *Never* attach development grade tools to a production device, 
most especially when you're dealing with a routing table. Not that I've 
ever taken down a live router in this manner[1], I'm just saying.. ;)

- billn

[1] All smirking current/past coworkers are kindly invited to stfu. =)



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