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MPLS Fundamentals by Luc De Ghein - CCIE No. 1897

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Troubleshooting CEF

When packets do not get to their destination in an MPLS network, it might be because CEF failed to label the packets correctly on the ingress PE router or forwarded them to the wrong adjacent router. You should have some technical troubleshooting skills to debug such CEF problems.

You can disable and enable CEF on the interface by using the command ip route-cache cef. Toggling CEF on the interface can often indicate whether the problem is with CEF. If the problem lies with the Layer 2 rewrite of the packets, you can check the adjacency information with the show adjacency command or clear the adjacency with the clear adjacency command. The debug command debug ip cef drops [access-list] tells you if IP packets are dropped on ...

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