RPKI validation codes: V valid, I invalid, N Not found Origin codes: i - IGP, e - EGP, ? - incomplete X best-external, a additional-path, c RIB-compressed, R RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, L 192.168.1.1/32 is directly connected, GigabitEthernet2ĬSR1000v# show ip bgp neighbors 10.0.0.2 advertised-routesīGP table version is 4, local router ID is 10.0.0.1 + - replicated route, % - next hop override, p - overrides from PfRġ0.0.0.0/8 is variably subnetted, 2 subnets, 2 masksĬ 10.0.0.0/30 is directly connected, GigabitEthernet1 O - ODR, P - periodic downloaded static route, H - NHRP, l - LISP Ia - IS-IS inter area, * - candidate default, U - per-user static route I - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2Į1 - OSPF external type 1, E2 - OSPF external type 2 To get started, let's configure the interfaces on our routers.Ĭodes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGPĭ - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area In a future blog post, we'll detail the differences between internal and external BGP.įigure 1: BGP Network Diagram Configure interfaces on both routers Check out the topology in the diagram below - we'll configure an internal BGP session (iBGP), which means that both BGP peers are part of the same autonomous network. The best way to learn is by example, so let's build a BGP session from scratch. "these are the routes that I'm aware of, tell me the routes that you are aware of"Ĭouple this concept with some route aggregation to avoid massive routing-tables and you can get a basic idea of how the Internet is built. Without these BGP sessions, no other networks in the world would know of your networks existence and vice-versa. You would then set up BGP sessions with other ISP companies and exchange route table information. To do so, you would need to obtain your own globally unique AS number. For example, imagine you wanted to start your own Internet Service Provider company. Why is this the case? Different networks around the world are divided into autonomous systems and allocated an AS number. Without BGP, the Internet would instantaneously collapse.
BGP, short for Border Gateway Protocol, is the most fundamental routing protocol on the Internet.