Prepend bgp question

[Amafsha1]

hello folks,

Let's say I have 2 sites, both use the same ISP and both advertise the same subnet 188.x.x.188.  They are in 2 different cities.

 I want site 1 to handle all in/out traffic for this subnet because it is primary and then set prepend for site 2 to handle the in/out if site 1 fails. 

My question:

How do I know (from standpoint of the internet) what the metrics are from both sites for the subnet that are being advertised.  I want to know if there is a command out there that can tell me what the world sees as the metrics for getting to these subnets at the 2 different locations. Is their a way to find out about this?  I want to becasue I just want to compare what the world sees as the more expensive route?  Does the world just see it as prepend of the AS, or do they actually see a string of numbers like eigrp metrics?  sorry, this might be a confusing question.  

[Richard Burts · Accepted solution]

We do not know much about your environment and that impacts our ability to give good suggestions. But some parts of your question we can answer. If you want to know how your network looks from the internet perspective there are various Internet looking glass sites that allow you to see your network from the Internet perspective. Google for Internet looking glass sites and you should be able to find one that will show you what you want to see. It is in the nature of BGP that only the best path is advertised to the Internet, so you will not see your second advertisement from these looking glass sites. 

The other thing we can address is your question about metrics. BGP does not use metrics in the way that EIGRP or OSPF do. So when you look for a route in the BGP Internet routing table you would see the AS path list but would not see things like bandwidth, or delay, or cost.

HTH

Rick

[Amafsha1]

Thanks Richard.  yeah, it was less of a technical question and more of a question of what the metrics look like from the outside standpoint and also what tool to use to find that out.  I just used the sprint tool and I can see the picture more clearly now.  

[Richard Burts]

I am glad that you see the picture more clearly now and that my suggestions were helpful. Yes the Internet looking glass sites do help us to see clearly how our networks are advertised. Thank you for marking this question as solved. This will help other participants in the forum to identify discussions which have helpful information. These forums are excellent places to ask questions and to learn about networking. I hope to see you continue to be active in the forum.

HTH

Rick