Segmentation is the practice of dividing one physical network into separate, isolated logical networks. A VRF (Virtual Routing and Forwarding) instance is the mechanism that makes this possible inside a router.
What it is
A VRF is an independent routing table living on the same device as others. Two VRFs can even use the same IP address ranges without conflict, because their tables never mix. Service providers use them to keep each customer’s traffic completely separate on shared infrastructure; enterprises and utilities use them to separate environments — for example, keeping operational technology apart from corporate IT.
Two concepts govern how routes are kept apart or deliberately shared:
- Route distinguisher — makes each customer’s addresses globally unique, even when they overlap.
- Route-targets — import/export rules that control exactly which VRFs can share which routes.
Why it matters
Segmentation is only as good as its configuration. A single mistaken route-target can leak one tenant’s routes into another’s — a serious isolation breach in a service-provider network, and a safety and compliance event in a utility. And because isolation is invisible in day-to-day operations, these mistakes can sit undetected until traffic crosses a boundary it never should have.
Regulators have taken notice. Frameworks for critical infrastructure increasingly require organisations not just to design segmentation, but to continuously prove it.
What good looks like
Good segmentation assurance attributes every route to the tenant or zone it belongs to, watches the import/export rules that enforce isolation, and flags any leak or bridging the moment it appears — turning “we believe it’s isolated” into ongoing, auditable proof.