346IPv6 MPLS L3VPN packet forwardingFigure 89 IPv6 MPLS L3VPN packet forwarding diagramAs shown in Figure 89, the IPv6 MPLS L3VPN packet forwarding procedure is as follows:1. The PC at Site 1 sends an IPv6 packet destined for 2001:2::1, the PC at Site 2. CE 1 transmits thepacket to PE 1.2. Based on the inbound interface and destination address of the packet, PE 1 searches the routingtable of the VPN instance. Finding a matching entry, PE 1 labels the packet with both inner andouter labels and forwards the packet out.3. The MPLS backbone transmits the packet to PE 2 by outer label. The outer label is removed fromthe packet at the penultimate hop.4. According to the inner label and destination address of the packet, PE 2 searches the routing tableof the VPN instance to determine the outbound interface and then forwards the packet out theinterface to CE 2.5. CE 2 forwards the packet to the destination by IPv6 forwarding.IPv6 MPLS L3VPN routing information advertisementThe IPv6 VPN routing information of a local CE is advertised to a remote peer PE in three steps:1. From the local CE to the ingress PE.2. From the ingress PE to the egress PE.3. From the egress PE to the remote peer CE.Then, a route is available from the local CE to the remote CE.Routing information exchange from the local CE to the ingress PEAfter establishing an adjacency with the directly connected PE, a CE advertises its IPv6 VPN routes to thePE.The routes between a CE and a PE can be IPv6 static routes, RIPng routes, OSPFv3 routes, IPv6 IS-ISroutes, or EBGP routes. No matter which routing protocol is used, the CE always advertises standard IPv6routes to the PE.Routing information exchange from the ingress PE to the egress PEAfter learning the IPv6 VPN routes from the CE, the ingress PE adds RDs and route targets for thesestandard IPv6 routes to create VPN-IPv6 routes, saves them to the routing table of the VPN instancecreated for the CE, and then triggers MPLS to assign VPN labels for them.
