Cisco 3845 Software Guide - Page 647

Chapter 29 Configuring IP Unicast Routing Configuring Multi-VRF CE all of the service-provider VPN routes. Each PE router maintains a VRF for each of its directly connected sites. Multiple interfaces on a PE router can be associated with a single VRF if all of these sites participate in the same VPN. Each VPN is mapped to a specified VRF. After learning local VPN routes from CEs, a PE router exchanges VPN routing information with other PE routers by using internal BGP (IBPG). • Provider routers or core routers are any routers in the service provider network that do not attach to CE devices. With multi-VRF CE, multiple customers can share one CE, and only one physical link is used between the CE and the PE. The shared CE maintains separate VRF tables for each customer and switches or routes packets for each customer based on its own routing table. Multi-VRF CE extends limited PE functionality to a CE device, giving it the ability to maintain separate VRF tables to extend the privacy and security of a VPN to the branch office. Figure 29-8 shows a configuration using Cisco ME switches as multiple virtual CEs. This scenario is suited for customers who have low bandwidth requirements for their VPN service, for example, small companies. In this case, multi-VRF CE support is required in the Cisco ME switches. Because multi-VRF CE is a Layer 3 feature, each interface in a VRF must be a Layer 3 interface. Figure 29-8 Switches Acting as Multiple Virtual CEs VPN 1 CE1 PE1 PE2 Service provider VPN 1 CE2 VPN 2 VPN 2 101385 CE = Customer-edge device PE = Provider-edge device When the CE switch receives a command to add a Layer 3 interface to a VRF, it sets up the appropriate mapping between the VLAN ID and the policy label (PL) in multi-VRF-CE-related data structures and adds the VLAN ID and PL to the VLAN database. When multi-VRF CE is configured, the Layer 3 forwarding table is conceptually partitioned into two sections: • The multi-VRF CE routing section contains the routes from different VPNs. • The global routing section contains routes to non-VPN networks, such as the Internet. VLAN IDs from different VRFs are mapped into different policy labels, which are used to distinguish the VRFs during processing. If no route is found in the multi-VRF CE section of the Layer 3 forwarding table, the global routing section is used to determine the forwarding path. For each new VPN route learned, the Layer 3 setup function retrieves the policy label by using the VLAN ID of the ingress port and inserts the policy label and new route to the multi-VRF CE routing section. If the packet is received from a routed port, the port internal VLAN ID number is used; if the packet is received from an SVI, the VLAN number is used. OL-23400-01 Cisco ME 3800X and 3600X Switch Software Configuration Guide 29-81