Virtual Routing and Forwarding (VRF) divides one physical router into multiple independent virtual routers. Each VRF maintains an isolated routing table, allowing service-provider infrastructure to carry several customers’ traffic while permitting overlapping private addresses. section 17.2
A basic VRF-lite deployment follows three steps:
- Create each VRF with ip vrf vrf-name in global configuration mode. section 17.2
- Configure routing separately for each VRF and verify the resulting routing tables. section 17.2
Configuring and testing isolated routing tables
Create C1_VRF, C2_VRF, and C3_VRF, then assign interfaces to them. The ordinary show ip route command shows no routes, while show ip route vrf C1_VRF displays connected and local routes for interfaces assigned to C1_VRF. A normal ping uses the default routing table and fails; ping vrf C1_VRF and ping vrf C2_VRF select the intended virtual router and succeed.
VRF is commonly used with MPLS Layer 3 VPNs, where provider edge routers maintain a separate routing table for each customer. VRF-lite provides the local virtualization model without the more advanced MPLS Layer 3 VPN implementation. Traffic remains isolated unless deliberately enabled through VRF leaking, which is beyond CCNA scope. section 16.1.2 section 17.2
