Chapter 1 About Cisco IP Solution Center
The Customer’s and Provider’s View of the Network
Figure 1-6 Service Provider’s View of the Network
VPN 10
CE
Seattle
VPN 15
Gizmos, Intl.
San Francisco
| Service provider network | VPN 10 | CE |
| Gadgets, Inc. |
| | | | |
| | BGP | | | New York City |
| | | | |
| BGP | MPLS core | PE-2 | |
| | | BGP | | |
| | PE-3 | | VPN 15 | |
| VPN 10 | VPN 15 | | |
| | | | CE |
| | | | | Gizmos, Intl. |
| | | | | London |
| | CE | CE | | |
Gadgets, Inc. | Gizmos, Intl. |
Chicago | Berlin |
About Provider Edge Routers (PEs)
At the edge of the provider network are provider edge routers (PEs). Within the provider network are other provider routers as needed (often designated as P routers) that communicate with each other and the PEs via the Border Gateway Protocol-Multiprotocol (MP-BGP). Note that in this model, the service provider need only provision the links between the PEs and CEs.
PEs maintain separate routing tables called VPN routing and forwarding tables (VRFs). The VRFs contain the routes for directly connected VPN sites only. (For more information about VRFs, see the “VPN Routing and Forwarding Tables (VRFs)” section on page 1-16). PEs exchange VPN-IPv4 updates through MP-iBGP sessions. These updates contain VPN-IPv4 addresses and labels. The PE originating the route is the next hop of the route. PE addresses are referred to as host routes into the core interior gateway protocol.
About Multi-VRF CEs
The Multi-VRF CE is a feature that provides for Layer 3 aggregation. Multiple CEs can connect to a single Multi-VRF CE (typically in an enterprise network); then the Multi-VRF CE connects directly to a PE. A Multi-VRF CE can be a Cisco router or a Cisco Catalyst® 3550 Intelligent Ethernet Switch.
The Multi-VRF CE functionality extends some of the functionality formerly reserved to the PE to a CE router in an MPLS VPN—the only PE-like functionality that this feature provides is the ability to have multiple VRFs on the CE router so that different routing decisions can be made. The packets are sent toward the PE as IP packets.
With this feature, a Multi-VRF CE can maintain separate VRF tables to extend the privacy and security of an MPLS VPN down to a branch office, rather than just at the PE router node.
Cisco IP Solution Center, 3.0: MPLS VPN Management User Guide, 3.0
