Exam 350-401 topic 1 question 756 discussion

C is correct

Cisco Express Forwarding (CEF) is a switching technology used in Cisco devices to improve packet forwarding efficiency. It is a Layer 3 IP switching technology that uses dedicated hardware processors (such as ASICs - Application-Specific Integrated Circuits) to make forwarding decisions based on information in the Forwarding Information Base (FIB) and Adjacency Table. CEF offloads packet switching from the main CPU, which allows for faster and more efficient packet forwarding. In contrast, process switching involves the main processor (CPU) of the router or switch making forwarding decisions for each packet. This method is less efficient and can result in higher CPU utilization, especially in high-traffic environments. Process switching doesn't rely on dedicated hardware processors for forwarding decisions. Option C accurately describes the difference between Cisco Express Forwarding and process switching, as CEF uses dedicated hardware processors, while process switching relies on the main CPU. The other options do not accurately describe the key differences between the two switching methods.

Distributed CEF (dCEF) mode - When dCEF is enabled, line cards maintain identical copies of the FIB and adjacency tables. The line cards can perform the express forwarding by themselves, and this relieves the main processor - Gigabit Route Processor (GRP) - of involvement in the switching operation. This is the only switching method available on the Cisco 12000 Series Router. https://www.cisco.com/c/en/us/support/docs/routers/12000-series-routers/47321-ciscoef.html

dedicated hardware processor means packet processing ASIC

I think C

C is correct

I would go with C

CEF uses CAM to store the FIB and the Adjacency Table. Process switching uses the RIB, which is stored in RAM. C to me is incorrect because CEF utilizes an ASIC, not a dedicated processor.

C) Correct https://www.networkfashion.net/l3-forwarding-techniques-process-switching-fast-switching-cef/ "When the forwarding engine is decoupled from the RP and located in the line cards, then the forwarding decision is made there and is not passed to the route processor. " However "dedicated hardware processors" is not the appropriate terminology, this answer fits best. There are different terms for this technology, like Superviser Engine, forwarding engine, L3 engine, Network Processing Unit...

A) Wrong -> An advantage of CEF is the lower CPU usage and not the lower memory usage https://community.cisco.com/t5/routing/enabling-cef-question/td-p/2041858 https://networkengineering.stackexchange.com/questions/48699/cisco-catalyst-switching-with-supervisor-and-line-cards dCEF: "When distributed Cisco Express Forwarding is enabled, line cards maintain an identical copy of the FIB and adjacency tables. The line cards perform express forwarding between port adapters, thus relieving the RP of involvement in the switching operation. " Same here: https://study-ccnp.com/cisco-express-forwarding-cef-overview/ B) Worng -> Adjacency table contains information mainly learned from from ARP table. https://www.networkfashion.net/l3-forwarding-techniques-process-switching-fast-switching-cef/ D) It is not worth mentioning.