Operation Manual – IPv4 RoutingH3C S7500E Series Ethernet Switches Chapter 5 BGP Configuration5-2z Supporting CIDRz Substantially reducing bandwidth occupation by advertising updating routes onlyand applicable to advertising a great amount of routing information on the Internetz Eliminating route loops completely by adding AS path information to BGP routesz Providing abundant routing policies to implement flexible route filtering andselectionz Easy to extend, satisfying new network developmentsA router advertising BGP messages is called a BGP speaker, which exchanges newrouting information with other BGP speakers. When a BGP speaker receives a newroute or a route better than the current one from another AS, it will advertise the route toall the other BGP speakers in the local AS.BGP speakers call each other peers, and several associated peers form a peer group.BGP runs on a router in one of the following two modes:z IBGP (Interior BGP)z EBGP (External BGP)BGP is called IBGP when it runs within an AS and is called EBGP when it runs betweenASs.5.1.1 Formats of BGP MessagesI. HeaderBGP has five types of messages:z Openz Updatez Notificationz Keep-alivez Route-refreshThey have the same header, as shown below:Figure 5-1 BGP message headerz Marker: The 16-byte field is used for BGP authentication. If no authenticationinformation is available, then the Marker must be all ones.
