Operation of CEF

When a packet enters the router, the router strips off the Layer 2 information. The router looks up the destination IP address in the CEF table (FIB), and it makes a forwarding decision. The result of this forwarding decision points to one adjacency entry in the adjacency table. The information retrieved from the adjacency table is the Layer 2 rewrite string, which enables the router to put a new Layer 2 header onto the frame, just before switching the packet out onto the outgoing interface toward the next hop. Figure 6-3 shows CEF forwarding an IP packet and the role of both the Layer 3 lookup of the destination IP address and the Layer 2 rewrite on the frame.

Figure 6-3 Layer 3 Lookup and Layer 2 Rewrite When Forwarding an IP Packet

Figure 6-3 Layer 3 Lookup and Layer 2 Rewrite When Forwarding an IP Packet

Micro Expression Master

Micro Expression Master

If You Could Read Everyone Life A Book You Can Have Better Career, Great Relationships And Become Successful. This Book Is One Of The Most Valuable Resources In The World When It Comes To Reading the smallest and tiniest body Language and know what people are thinking about.

Get My Free Ebook


Post a comment