4 Replies Latest reply: Apr 28, 2012 11:38 PM by ibrahim mohho RSS

    defference between aCEF and dCEF

    ibrahim mohho

      hi

      can you ell me in deatils what are the defferences between aCEF and dCEF

        • 1. Re: defference between aCEF and dCEF
          Mahdi

          Hi ibrahim,

           

          Accelerated CEF (aCEF)—CEF is distributed across multiple Layer 3 forwarding engines, typically located on Catalyst 6500 line cards. These engines do not have the capability to store and use the entire FIB, so only a portion of the FIB is downloaded to them at any time. This functions as an FIB “cache,” containing entries that are likely to be used again. If FIB entries are not found in the cache, requests are sent to the Layer 3 engine for more FIB information. The net result is that CEF is accelerated on the line cards, but not necessarily at a sustained wire-speed rate.

           

          Distributed CEF (dCEF)—CEF can be distributed completely among multiple Layer 3 forwarding engines for even greater performance. Because the FIB is self-contained for complete Layer 3 forwarding, it can be replicated across any number of independent Layer 3 forwarding engines. The Catalyst 6500 has line cards that support dCEF, each with its own FIB table and forwarding engine. A central Layer 3 engine (the MSFC3, for example) maintains the routing table and generates the FIB, which is then dynamically downloaded in full to each of the line cards.

           

          Reference: CCNP SWITCH 642-813 Official Certification Guide

           

          HTH,

          • 2. Re: defference between aCEF and dCEF
            ibrahim mohho

            thanks but i asked because i read this from book and i need more explaintion

            what dose line card mean is it interface ?

            and what is the portion of FIB belong it ?

            and the FIB portion in the line card does it depends on mac teble for this laine card ?

            if some body has an article for complete this i will be thankful

            • 3. Re: defference between aCEF and dCEF
              Mahdi

              for your first question : No it does not mean interface, it means supervisor engine like supervisor 720

               

              second question: your answer is in the text -> containing entries that are likely to be used again

               

              Third question: as I said in previous answer line card means supervisor engine and does not have mac address.

               

              HTH

              Mahdi

              • 4. Re: defference between aCEF and dCEF
                ibrahim mohho

                thanks alot ...