LEARN. PRACTICE. GROW.Concept and mechanism
A VRF maintains its own routing instance. A route found in the global table does not demonstrate that traffic received in another VRF can use it. Record context, source, and return path when investigating connectivity. Route leaking enables exceptions between instances, but making routes available does not replace service authorization. A tunnel also does not imply encryption: GRE encapsulates, while confidentiality needs appropriate protection such as IPsec configured for the specific design. VXLAN adds overhead. The underlay must support sizes required across the entire path within equipment limits. Do not confuse a successful small ping with proof that all application packet sizes can traverse.
Guided application
In a fictional shared-DNS case, an application needs a service in another VRF. Define required prefixes, flow controls, and response, also checking access that should remain denied. Importing every corporate route broadens scope without demonstrating need. Device virtualization requires similar attention to boundaries: a type-one hypervisor runs on hardware, while type two depends on a host operating system. In both cases, two VMs on one host still share that failure domain. The PM should request placement and recovery evidence as well as instance counts. An apparently redundant logical design can depend on one physical component, one power supply, or the same storage.
The route exists globally; the application still lacks a path in VRF FUNDS.
Common pitfalls
Tunnel as encryption; route as authorization; VM as independent hardware; local MTU as validated path.
Related topics: Architecture and surviving capacity · Switching and adjacency formation · Routing and IP services
Identify actual forwarding, protection, and failure boundaries.
Reference: VRF route leaking · 350-401 ENCOR v1.2, effective 2026-03-19; core component of CCNP Enterprise