I had this question recently posed to me in an interview:
You are a cloud services provider.
You have multiple remote customers separated by any number of AS's from you.
You advertise your BGP prefixes along an optimal path and a sub-optimal path where, receiving both, all customer routers will by default choose the optimal path.
For specific reasons you want to force customer A to install prefixes learned through the sub-optimal path, without affecting any other customers.
You have control over your network only, and no control over any customer or transit networks.
How would you do this?
