Why do we need i-BGP for the routes when we have the IGP protocols (OSPF, IS-IS) for internal communication within the AS?
Why do we need i-BGP for the routes when we have the IGP protocols (OSPF, IS-IS) for internal communication within the AS? IGPs like OSPF or ISIS, are link-state protocols that give us all the information of the network and allow for very interesting convergence options and traffic engineering options. Whereas, BGP knows a very limited view of the network as a whole because BGP handles very well filtering and modifying routing information. See, the traffic in a network can be divided into 4 categories. • Ingress: traffic arriving from outside the network, destined for hosts within the network. • Egress: traffic originating inside the network destined for hosts outside the network. • Internal: traffic where both the origin and destination are within the network. • Transit: traffic where both the origin and destination are outside the network. The IGP normally carries internal routes, so it can be used to directly route ingress and internal traffic, but what about egress and transit tra