MPLS Troubleshooting Tips for Cisco and Juniper

MPLS Troubleshooting Tips for Cisco and Juniper

Basic MPLS Troubleshooting Tips

1. Verifying MPLS Configuration:

  • Cisco:
    • Use show mpls interfaces to verify that MPLS is enabled on the correct interfaces.
    • Check show mpls ldp neighbor to ensure that Label Distribution Protocol (LDP) neighbors are discovered, and that the session is up.
  • Juniper:
    • Use show mpls interface to check MPLS status on interfaces.
    • Utilize show mpls ldp session to confirm LDP neighbor sessions.

2. Checking Label Switch Paths (LSP):

  • Cisco:
    • Use show mpls ldp bindings to display local and remote label bindings.
    • show mpls forwarding-table helps to inspect the labels being forwarded and their corresponding next-hops.
  • Juniper:
    • Use show mpls lsp extensive to get detailed information about the LSPs.
    • show route table mpls.0 to view the label-switched routes.

3. Ensuring Proper Route Distribution:

  • Cisco:
    • Verify routing protocols are correctly redistributing routes with show ip route and show ip protocols.
    • Ensure that MPLS labels are being properly assigned by checking show mpls forwarding-table.
  • Juniper:
    • Check routing information with show route forwarding-table family mpls.
    • Ensure correct route redistribution settings with show route protocol.

4. Troubleshooting MPLS VPNs:

  • Cisco:
    • For issues with VRF (Virtual Routing and Forwarding), use show ip vrf and show ip route vrf [vrf-name].
    • Verify MPLS VPN label distribution and path information using show mpls forwarding-table vrf [vrf-name].
  • Juniper:
    • Check VRFs using show route table [vrf-name].inet.0.
    • Look at the VPN labels with show route table [vrf-name].inet.0 detail.

5. Utilizing Cisco debug and Juniper traceoptions:

  • Cisco:
    • In-depth troubleshooting can be performed by enabling debugging: debug mpls ldp for LDP-related issues or debug mpls traffic-eng for traffic engineering problems.
  • Juniper:
    • Use traceoptions under the MPLS or routing protocol configuration to capture more detailed logs for troubleshooting.

6. Common Pitfalls and Checks:

  • Both Cisco and Juniper:
    • Ensure there are no MTU mismatches across MPLS-enabled interfaces, as this can disrupt proper LSP formation.
    • Regularly check for software or firmware updates that address known bugs or add enhancements to MPLS features.

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