BGP basics

BGP (Border Gateway Protocol) is a routing protocol with two types: iBGP (internal BGP) for route exchange within the same autonomous system, where routes are only exchanged between directly connected neighbors, and eBGP (external BGP) for route exchange between different autonomous systems, where all learned routes are propagated between peers. A critical challenge in BGP is the next hop resolution problem, where routes may be learned but cannot be used for forwarding if the next hop is unreachable. This is resolved using the 'next hop self' command on route reflectors for iBGP and on eBGP peers to ensure routes appear to come from the correct gateway, enabling proper traffic forwarding across the network.