When is a virtual routing and forwarding (VRF) instance typically used?

According to Juniper Networks' documentation on campus fabric and EVPN-VXLAN architectures, a Virtual Routing and Forwarding (VRF) instance—conceptually referred to within the Junos OS as a routing instance—is typically used to provide macro-segmentation by logically separating a single physical network into multiple, isolated virtual networks.2 In the context of a modern campus fabric managed by Juniper Mist, VRFs allow network administrators to create distinct routing domains that maintain their own independent routing and forwarding tables.3

This separation is essential for multitenancy and security.4 For example, an organization might use one VRF for "Corporate_IT" and another for "Guest_WiFi" or "IoT_Devices". Because each VRF operates with its own routing table, traffic belonging to one instance is completely isolated from traffic in another by default; packets cannot travel between VRFs unless an administrator explicitly configures "route leaking" or directs the traffic through a stateful firewall for security inspection. This architectural approach also permits the use of overlapping IP address spaces, as the routing decisions for one tenant do not interfere with the address entries of another.5

In a Juniper Mist-driven campus fabric (such as Core-Distribution or IP Clos), the Mist portal streamlines the creation of these VRF instances as part of the fabric workflow.6 Once a VRF is created, specific VLANs (and their corresponding IRB interfaces) are assigned to it, ensuring that Layer 3 gateways are placed in the correct logical domain. While the underlay network (Option D) is responsible for providing the physical reachability (loopback to loopback) between switches using a protocol like eBGP, the overlay network leverages VRFs to deliver the actual isolated user services.