MPLS Troubleshooting Tips

Anyone of you having difficulty in troubleshooting MPLS as a beginner?
I did some research and take notes for myself and now it is for you to do reference as well.

MPLS troubleshooting can be divided into two main steps:

1) Verify routing information flow
2) Verify proper data flow

- Routing information flow troubleshooting requires verification of end-to-end routing information propagation between CE routers.
- Verification of the routing information flow should be done systematically, starting at the routing ingress CE and moving to the egress CE.
- Verification of the data flow should be done systematically, starting at the data flow ingress CE and moving to the egress CE.

There are three things to perform basic MPLS troubleshooting.
They are,
1) Preliminary steps in MPLS VPN Troubleshooting:
- Is CEF enabled?
- Are labels for IGP routes generated and propagated?
- Are large labeled packets propagated across the MPLS backbone (maximum transmission unit issues)?

2) Verify the routing information flow:
- Are CE routes received by a PE?
- Are routes redistributed into MP-BGP with proper extended communities?
- Are VPNv4 routes propagated to other PE routers?
- Is the BGP route selection process working correctly?
- Are VPNv4 routes inserted into VRFs on other PE routers?
- Are VPNv4 routes redistributed from BGP into the PE-CE routing protocol?
- Are IPv4 routes propagated to other CE routers?

3) Verify proper data flow:
- Is CEF enabled on the ingress PE router interface?
- Is the CEF entry correct on the ingress PE router?
- Is there an end-to-end label switched path tunnel (LSP tunnel) between PE routers?
- Is the LFIB entry on the egress PE router correct?

Do you have/know something that I missed out in my above list? Please assist me by letting know. Thanks.

Have a good day.
(Be knowledgeable, pass it on then)

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