Difference Between CEF and Process Switching

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CEF ( Cisco Express Forwarding) and process switching are two methods used by Cisco routers to forward packets between networks. Here's a detailed explanation of the differences between them:

CEF: Cisco Express Forwarding (CEF) is a high-performance, Layer 3 switching technology that is used to forward packets through a router. CEF builds a Forwarding Information Base (FIB) and an adjacency table. The FIB contains information about the destination networks, while the adjacency table contains information about the next hop for each destination. When a packet arrives at a router, CEF looks up the destination address in the FIB and finds the next hop in the adjacency table. It then forwards the packet to the next hop without involving the router's CPU, resulting in faster packet forwarding.

Advantages of CEF:

• Faster packet forwarding than process switching
• Reduced CPU utilization
• Provides load balancing and redundancy
• Supports quality of service (QoS)

Process Switching: Process switching is a method used by Cisco routers to forward packets when CEF is not enabled. When a packet arrives at a router, the router interrupts the CPU to process the packet. The CPU looks up the destination address in the routing table and determines the next hop for the packet. The router then encapsulates the packet in a new frame and forwards it to the next hop.

Disadvantages of process switching:

• Slower packet forwarding compared to CEF
• Higher CPU utilization
• No load balancing or redundancy
• Does not support QoS

In summary, CEF is a more efficient and faster packet forwarding method than process switching. CEF uses the FIB and adjacency table to make forwarding decisions, while process switching involves the router's CPU to process each packet, resulting in slower packet forwarding and higher CPU utilization.