A tax-assessor VPN complaint shows missing labels between PEs even though VPNv4 routes look present on the route reflector. What should operators verify first as the foundation for MPLS L3VPN forwarding?
Select an answer to reveal the explanation.
Short Explanation
No solid road, no delivery truck — VPNv4 routes on a reflector are just the address book. The underlay IGP plus LDP (or SR) has to build the labeled highway between PEs first. Fix that foundation before blaming BGP VPN exchange.
Full Explanation
MPLS L3VPN data-plane success requires a healthy underlay: IGP reachability to PE loopbacks and label distribution (commonly LDP) that builds transport LSPs between those PEs. Control-plane VPNv4 presence on a route reflector does not prove labeled forwarding works. Matching RDs or stuffing Internet defaults into VRFs does not create LSPs. Confirm IGP/LDP underlay health before escalating to PE-CE or RT policy issues.