Virtual routers and virtual routing and forwarding (VRF)

A virtual router is a network virtualization feature that

  • maintains separate routing tables for groups of interfaces

  • provides clean separation in the traffic flowing through the device, and

  • implements the "light" version of Virtual Routing and Forwarding, or VRF-Lite, which does not support Multiprotocol Extensions for BGP (MBGP).

Virtual router capabilities and configuration

Virtual routers provide support to two or more distinct customers over a common set of networking equipment. You can also use virtual routers to provide more separation for elements of your own network, for example, by isolating a development network from your general purpose corporate network.

When you create a virtual router, you assign interfaces to the router. You can assign a given interface to one, and only one, virtual router. You would then define static routes, and configure routing protocols such as OSPF or BGP, for each virtual router. You would also configure separate routing processes over your entire network, so that routing tables on all participating devices are using the same per-virtual-router routing process and tables. Using virtual routers, you create logically-separated networks over the same physical network to ensure the privacy of the traffic that runs through each virtual router.

Because the routing tables are separate, you can use the same, or overlapping, address spaces across the virtual routers. For example, you could use the 192.168.1.0/24 address space for two separate virtual routers, supported by two separate physical interfaces.

Note that there are separate management and data routing tables per virtual router. For example, if you assign a management-only interface to a virtual router, then the routing table for that interface is separate from the data interfaces assigned to the virtual router.

Virtual routers and dynamic VTI

You can create virtual routers, associate dynamic VTIs with these virtual routers, and extend the capabilities of dynamic VTIs in your network. You can associate dynamic VTIs either with global or user-defined virtual routers. You can assign a dynamic VTI to only one virtual router. For more information, refer to Virtual Routers and Dynamic VTI.