BGP AS design

[ccs10021]

Is this a legal AS design ( diagram is attached) ?  I'm not sure if the dis-contiguous AS 100 is an issue. 

I posted this on another site....

Is there potential for issues when advertising different prefixes from different locations but in same AS?

Router 'A' in New York will advertise prefix x.x.x.x/24 and Router 'B' in London will advertise y.y.y.y/24.

Both of the routers will exist in the same AS(AS 100). They will not maintain an iBGP peering with each other(see attached diagram).

Thanks!

[Georg Pauwen]

Hello,

this shouldn't be a problem, just make sure you don't advertise the same prefixes from both sites in AS100, and configure both RouterA and RouterB with the 'allowas-in' feature on their neighor statements to ISP A and ISP B, otherwise RouterA and RouterB won't see each others advertised networks ( due to the fact that BGP rejects any routing update in which its autonomous system number is already present)...

[paul driver]

Hello

The question is why would you have such a design if  two sites with the same AS have no communication to each other (igp etc.). It wouldn't be recommended, Having the same AS in two different locations which are totally separate wouldn't be unique to each location, and thats what a BGP ASN is designed to do, unless its designed that way to cut down of igbp peering and to utilize Router reflector or confederations which is very unlikely just for two sites.

So regards your OP I would say yes it is a bad design.

res

Paul