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Cisco · SPCORIntermediate

MPLS L3VPN: Customer Routes Missing

MP-BGP is carrying the prefixes and the VRF is empty. Find where they are being filtered, live, right below.

Interactive simService ProviderMPLSL3VPN

Symptom

The MPLS core is up and MP-BGP is peering, but two sites in the same L3VPN still can't see each other's routes.

Your mission

Inspect, recover, then verify

Format

Cisco IOS CLI

Start interactive labSee the investigation plan ↓Need a hint? Reveal the root cause ↓
MPLS L3VPN: Customer Routes Missing

Investigate before you configure.

Use the CLI evidence to isolate the fault, make the smallest safe correction, then verify the network state changed.

Observe the symptom and link state.

Diagnose by comparing the protocol evidence.

Verify the expected device state and confirm the original symptom is resolved.

Console access: PE2 (receiving) · PE1 (originating)

This workspace stacks for portrait phones. Rotate to landscape for the full split-screen console.

Need a hint?

Reveal the root cause when you're ready.

Try the investigation first, then use this as your escape hatch, not a dead end.

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Lab debrief

Turn the session into a repeatable troubleshooting pattern.

Use this reference after your attempt: first explain the symptom, then verify the evidence, then confirm the repair.

The problem

Two customer sites in the same L3VPN can't reach each other. The MPLS core is up, LDP labels are exchanged, and each PE learns its own local CE routes, but the remote site's prefixes never appear in the customer VRF at the other PE.

What you'll practice

  • Build an MPLS core with LDP label distribution
  • Establish MP-BGP VPNv4 sessions between PE routers
  • Configure per-customer VRFs with route-target import/export
  • Diagnose why VPNv4 routes fail to install in a VRF
  • Verify end-to-end CE-to-CE reachability across the L3VPN

The topology

A provider core of P and PE routers runs MPLS with LDP, and two PEs each attach to a customer CE inside one L3VPN. Labels switch across the core while MP-BGP carries the customer prefixes as VPNv4, so a route-target mismatch shows up as missing customer routes, not a broken core.

Commands to run yourself

The real diagnostic commands for this lab, copy-paste ready. Run these in the same order to reproduce the investigation on your own session.

Check the core's label distribution
show mpls ldp neighbor
Confirm the VPNv4 session
show bgp vpnv4 unicast all summary
Compare the VRF route-targets
show vrf detail CUST

Topology diagram

Fact-checked references

The commands and behaviour in this lab were checked against these primary references.

Frequently asked

Is the core actually broken?

No, and that's the lesson. LDP and MP-BGP can be perfectly healthy while a route-target mismatch quietly filters the customer's VPNv4 routes at import.

Does this map to SPCOR?

Yes. MPLS, LDP, MP-BGP VPNv4 and L3VPN are core Cisco Service Provider (SPCOR) topics, exercised here on a real multi-router core.

Ready to run this lab yourself?

No setup, no image sourcing. Book a session or ask for a live demo.

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