BGP and OSPF. How do they interact?
BGP (Border Gateway Protocol) only handles the exterior side of network routing. There is also interior routing.The most widely used interior gateway routing protocol is OSPF (Open Shortest Path First). Let's analyze the most common case: a network running BGP as the external gateway protocol and OSPF as the internal gateway protocol, and look at how the routing duties are divided over two protocols and how they interact. Read the full article on http://www.noction.com/blog/bgp_and_ospf_interaction