Operation Manual – Routing ProtocolH3C S5600 Series Ethernet Switches Chapter 5 BGP Configuration5-1Chapter 5 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 Examplez Troubleshooting BGP ConfigurationNote:z The term router in this chapter refers to a router in a generic sense or an Ethernetswitch running a routing protocol.z Unless otherwise noted, BGP in the following sections refers to BGP-4.z The BGP-related functions are unavailable to devices with the Intelligent ResilientFramework (IRF) fabric function enabled.5.1 BGP OverviewBorder gateway protocol (BGP) is a dynamic routing protocol designed to beemployed among autonomous systems (AS). An AS is a group of routers that adoptthe same routing policy and belong to the same technical management department.Four versions of BGP exist: BGP-1 (described in RFC1105), BGP-2 (described inRFC1163), BGP-3 (described in RFC1267), and BGP-4 (described in RFC1771). Asthe actual internet exterior routing protocol standard, BGP-4 is widely employedbetween internet service providers (ISP).BGP is featured by the following.z Unlike interior gateway protocols (IGP) such as OSPF (open shortest path first),RIP (routing information field), and so on, BGP is an exterior gateway protocol(EGP). It does not focus on discovering and computing routes but controlling theroute propagation and choosing the optimal route.z BGP uses TCP as the transport layer protocol (with the 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.
