I have this scenario (on the drawing) set up in a lab environment. We have 2 core routers with customers connected. We have 2 border routers. when customer A hits Core router 1 and goes out its default gateway, if it has the preferred route going out it has no problem. if it finds that the preferred route is on the other side on border router 2- it gets sent back to core router 1 (the correct path). But that router's default route points it back to border 1- causing a loop. How can I fix this without having the core routes handle all the internet routes?