Operation Manual – Routing ProtocolH3C S7500 Series Ethernet Switches Chapter 6 BGP Configuration6-1Chapter 6 BGP ConfigurationWhen configuring BGP, go to these sections for information you are interested in:z BGP Overviewz BGP Configuration Task Listz Displaying and Maintaining BGP Configurationz BGP Configuration Examplesz Troubleshooting BGP Configuration6.1 BGP Overview6.1.1 Introduction to BGPBorder gateway protocol (BGP) is a dynamic routing protocol designed to be usedbetween autonomous systems (ASs). An AS is a group of routers that adopt the samerouting policy and belong to the same technical management department.Four versions of BGP exist: BGP-1 (described in RFC 1105), BGP-2 (described inRFC 1163), BGP-3 (described in RFC 1267), and BGP-4 (described in RFC 1771). Asthe actual Internet exterior routing protocol standard, BGP-4 is widely employedbetween Internet service providers (ISPs).Note:Unless otherwise noted, BGP in the following sections refers to BGP-4.BGP has the following features:z Unlike interior gateway protocols (IGPs) such as OSPF (open shortest path first)and RIP (routing information protocol), BGP is an exterior gateway protocol(EGP). It does not focus on discovering or calculating routes but controlling theroute propagation and choosing the optimal route.z BGP uses TCP (transport control protocol) as the transport layer protocol (withthe port number being 179) to ensure reliability.z BGP supports classless inter-domain routing (CIDR).z With BGP employed, only the changed routes are propagated. This savesnetwork bandwidth remarkably and makes it feasible to propagate large amountof route information across the Internet.z The AS path information used in BGP eliminates route loops thoroughly.
