multiple BGP AS on router

Answered Question

I'm rather new to BGP and am looking at redesigning a section of our global WAN, but have found myself stuck. North America WAN is routing bgp over mpls. We have two locations in South America, one connected to the North America WAN, the other connected via a new mpls circuit from a different provider (SA)to the first South America location. Currently the location that has the new mpls circuit (P) is using all static routes to route traffic to the other South American location (JSA), which then connects to another router in the same location (JNA) back to the North America WAN (NA):


(NA) - (JNA) - (JSA) - (SA) - (P)


First, I am planning on consolidating the J location to one physical router:

(NA) - (J) - (SA) - (P)


Not a big deal there.

Next I would like to implement a routing protocol in South America WAN (SA) to avoid the constant need of updating static routes, etc if new facilities open and connect via that provider. This is challenging me as I will probably need to route BGP between the two providers. Could I run two bgp processes on the (J)router, one for each of the two autonomous systems (for NA and for SA), and then bidirectionally redistribute the routes between the two processes?

(NA)-(BGP65500 J BGP65600)-(SA)-(BGP65600 P)

Or, is this redistribution even necessary? Would the routing occur via eBGP between the two processes as they would simply be routes between two autonomous systems?

I suppose one final option would be to keep both routers in place and run the NA BGP AS on JNA and implement the SA BGP AS on JSA and P:


NA)BGP65500(JNA) BGP65600(JSA)BGP65600(P)



It would have been nice if they would have ordered a circuit from the same provider and I could implement BGP on the same private AS, but I have to deal with what I've got. I realize that this post has gotten rather lengthy, and probably quite convoluted. I've attached a drawing to help illustrate the options I am looking at. Any help would be greatly appreciated.



Attachment: 
Correct Answer by Harold Ritter about 9 years 11 months ago

Andy,


You can only run one BGP process per router. The AS used by this process is configured with the "router bgp xxx" command, where xxx is the AS number you want to use.


There is a feature that you can use though that will allow you use a different AS number for a specific peer. This feature is called local-as and should allow you to do what you want.


Please refer to the following URL for more information on how to use this feature:


http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00802c07ac.html#wp1045321


Hope this helps,

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Correct Answer
Harold Ritter Thu, 05/24/2007 - 04:45
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  • Cisco Employee,

Andy,


You can only run one BGP process per router. The AS used by this process is configured with the "router bgp xxx" command, where xxx is the AS number you want to use.


There is a feature that you can use though that will allow you use a different AS number for a specific peer. This feature is called local-as and should allow you to do what you want.


Please refer to the following URL for more information on how to use this feature:


http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00802c07ac.html#wp1045321


Hope this helps,

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