BGP and OSPF Interaction

BGP and OSPF work together in a network to provide reachability (that is, routing) information to routers about networks outside the OSPF network. In a provider network, BGP populates the routing table, with the address of the eBGP neighbor, as the next hop for routes to exterior autonomous systems. OSPF is used within the AS to provide the internal routing throughout the network; BGP and OSPF rely upon each other at various places to provide optimal and effective routing.

All this is interesting conceptually, but take a moment to visualize a possible network that uses both OSPF and BGP and connects to the Internet through two different providers at two different locations. This network topology and configuration is common ...

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