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MPLS Fundamentals by Luc De Ghein - CCIE No. 1897

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Why Is CEF Needed in MPLS Networks?

Concerning MPLS, CEF is special for a certain reason; otherwise, this book would not explicitly cover it. Labeled packets that enter the router are switched according to the label forwarding information base (LFIB) on the router. IP packets that enter the router are switched according to the CEF table on the router. Regardless of whether the packet is switched according to the LFIB or the CEF table, the outgoing packet can be a labeled packet or an IP packet. Figure 6-1 shows the difference between a lookup in the CEF table and in the LFIB.

Figure 6-1. Lookup in CEF Table Versus Lookup in LFIB

When an IP ...

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