To support multiple customer routing tables each routing instance is placed into a concept of a virtual router. This is called the VRF table feature, VRFs store customer routes separately on different customer VPNs, this allows all sites in the same VPN to communicate and share routes while keeping other customer routing instances separate.
Typically each customer gets their own VRF routing instance in an MPLS aware router, some complex designs for a single customer may require multiple VRFs, for varying reasons. (ie route advertisements, internet routing, etc..)
Each VRf has three components:
- IP routing table (RIB)
- CEF FIB populated from VRF RIB
- Seperate instance of routing protocol used to exchange routes with CEs that need to be supported by the VRF