An engineer configured a company's multiple area OSPF Head Office router and Site A Cisco routers with VRF lite. Each site router is connected to a PE router of an MPLS backbone. After finishing…

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Explanation

This question tests knowledge of OSPF VRF lite behavior and the required 'capability vrf-lite' command. Without it, an OSPF process running inside a VRF will suppress inter-area and external LSA types, causing exactly the symptom described.

Approach. The fix is to add 'capability vrf-lite' under 'router ospf 1 vrf abc' on both the Head Office and Site A routers. When Cisco IOS runs an OSPF process inside a VRF, it assumes by default that the router is an MPLS-aware PE device and applies PE-specific LSA filtering rules - this silently blocks Type 3 (inter-area summary), Type 4 (ASBR summary), Type 5 (external), and Type 7 (NSSA external) LSAs from being installed in the RIB. The 'capability vrf-lite' command explicitly declares that this OSPF instance is operating in a VRF lite (non-MPLS, CE-side) context, lifting those restrictions and allowing all LSA types to propagate and install normally. Without this single command the adjacency can still form, but the routing table inside the VRF will be empty of everything beyond Type 1/2 LSAs - matching the exact failure described in the scenario.

Concept tested. OSPF VRF lite - the mandatory 'capability vrf-lite' command under a VRF-scoped OSPF process; understanding why its absence suppresses Type 3/4/5/7 LSA installation even when the OSPF adjacency is up.

Reference. Cisco IOS IP Routing: OSPF Configuration Guide - 'OSPF VRF-Lite Support'; also covered in CCNP ENCOR (350-401) topic: Advanced OSPF and VRF-Aware Routing

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