3Com Switch 8800 Configuration Guide Chapter 37 BGP/MPLS VPN Configuration37-5RD IPv4 address ... ERT1 ERT2 ... ERTnERT: Export Route TargetsImport Route Targets:( IRT1, IRT2, ... ,IRTm )MPLS VPN RouteFigure 37-3 Route filtering through matching VPN Target attributeNote:The routes for other VPNs will not appear in the VPN's routing table by using VPNTarget attribute to filter routing information received at PE router, so the CE-transmitteddata will only be forwarded within the VPN.37.1.2 BGP/MPLS VPN ImplementationBGP/MPLS VPN works on this principle: It uses BGP to propagate VPN private routinginformation on carrier backbone network, and uses MPLS to forward VPN servicetraffic.The following are introductions to BGP/MPLS implementation from two aspects:advertising VPN routing information and forwarding VPN packets.I. Advertising VPN routing informationRouting information exchange has the following four types:1) Between CE and PEA PE router can learn routing information about the CE connected to it through staticroute, RIP (supporting multi-instance), OSPF (supporting multi-instance) or EBGP, andimports it in a vpn-instance.2) Between ingress PE and egress PEThe ingress PE router uses MP-BGP to send information across public network: Itadvertises routing information learned from CE to the egress PE router (with MPLSlabel) and learns the CE routing information learned at the egress PE router.The internal connectivity among the VPN internal nodes is ensured through enablingIGP (for example, RIP and OSPF) or configuring static routes on the PEs.LSP setup between PEs
