City public-works users on an L3VPN report loss of connectivity. Which troubleshooting order best separates underlay from overlay problems?
Select an answer to reveal the explanation.
Short Explanation
Fix the road, then the address book, then the driveway — underlay LSP, MP-BGP VPNv4, then PE-CE. Jumping straight into CE debugs when labels are broken wastes a public-works afternoon. Layer the checks so each layer earns the next.
Full Explanation
Methodical MPLS L3VPN troubleshooting separates planes: confirm IGP/LDP (or SR) transport LSPs between PEs, confirm VPNv4 prefixes and RT import on the PEs, then validate PE-CE protocol exchange and VRF forwarding. Starting with RT rewrites or CE-only debugs skips foundational failures. PHP tweaks are not a first step. That ordered separation speeds isolation for civic VPN outages.