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New Member

BGP

I have 2 ISP's. Is there a quick way to see which IP routes will go out which ISP.

My BGP path tables look as if everything goes out over UUNET yet I know data goes out my other ISP.

6 REPLIES
Silver

Re: BGP

If I understand your question correctly, look for the next AS number for the respective ISP. UUNet is AS 701 for North America but I dont know if you will be able to see it as 701. You may also benfit from pipe operator that works like grep.

Thanks.

New Member

Re: BGP

Hi Phil,

Its not 100% what your question is ,but if the question is "how can i tell what ip routes i am advertising to BGP peer x.x.x.x" then the answer is use the command "sh ip bgp neighbour x.x.x.x advertised-routes". This will tell you what your sending to x.x.x.x.

Apologies in advance if I have misunderstood your question. If not I hope this helps.

Jonathan

New Member

Re: BGP

The route table shows which networks are reached via which next hop. That's not to say that return traffic comes back on the same path - that depends on what your ISPs do with your routes.

New Member

Re: BGP

The benefit of multihoming is redundancy as u r connected to 2 ISP's. UUnet has probably better routers, better physical Links or more NAP connections. You should not expect the traffic load to be 50/50 unless you want to manipulate route preferences and balance your traffic across the 2 links.

If u want to know what route traffic is taking then trace traffic to destinations you usualy link to.

New Member

Re: BGP

You can try this:

sh ip bgp neighbor X.X.X.X routes

This will show you what routes that particualr neighbor is sending to you

any route with a ">" in the first colum is a route BGP has determined to be

THE BEST and is the route currently being used in the IP forwarding table (routing table)

New Member

Re: BGP

correction the ">" will be in the second colum you should see a "*" in the first colum which means it is a valid reachable route (I think thats what * means)

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