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BGP Island? Does an AS need to be internally connected?

Does an AS need to be internally connected?

Say I have multihomed Facility A with AS A announcing PI Network A in City A to Peer X and Peer Y. Everyone is happy.

Now I set up a second site: Facility B, PI Network B, City B. It will only announce Network B to it's peers, but...

Can I use the same AS A, and, perhaps crucially, multihome to the same two peers, X & Y?  (Not the exact same neighbors, but X & Y are national networks and use their usual AS #s.) And B is an island. I'm just a content provider with two cages in different states. I'm not a network and site A and B have no circuit or tunnel connectivity.

Will this even work?  Will I get traffic for site A dumped off at site B because the AS is the same?  Even if I advertise only local networks to peers?  Is it even kosher to make inconsistent AS announcements?

Another way to say this is: say Site A is up and running. Do I need a different AS number to light up a new (island, different network #) Site B?

My understanding of the BGP RFC is that every transit router has the well-known mandatory NEXT_HOP attribute attached to every AS in the path in their RIB, so in theory, my peers know which exit to take and everything will work.

But my worry is that I will run into the "my network my rules" paradigm. Since my immediate peers are the same, their packet flow is up to them, RFC or no RFC.  (And there is a worrying SHOULD in a crucial spot in that RFC.)  I can certainly imagine them reasoning:

Why should I transport their traffic parallel to their network? Why not just dump their traffic at the nearest point I can reach their AS and let them carry the freight?

Transit peers must make that kind of decision all the time.

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