E-series routers can support up to 1,000 forwarding tables; that is, up to a total of 1,000 VRs and VPN routing and forwarding (VRF) instances. Each VRF has a forwarding table. A network device attaching to a router detects a router interface. The attaching device has no notion of the virtual router behind the interface.
For example, a physical ATM link may have circuits that are connected to different VRs. The physical and data link layers are not aware that there are multiple router instances. See Figure 31.
Figure 31: Virtual Routers
VRs and VRFs are tools for implementing VPNs.
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