Hello Aman,

CFC cards use the centralized forwarding done by the Sup-engine.With CFC, all the forwrading decisions, packet re-writing is done by the PFC on the supvervisor engine.

You need DFC's when you want a complete distributed architecture on the 6500 chassis.

6500 gives you 30 Mpps per system without the DFC's on the classic/fabric-enabled/Fabric only card's. If you have an environment where you have a high traffic usage, then you need DCEF cards. With DFC's daughter card on the module, you get 48 MPPS per slot and the overall performcace of the chassis increases upto 400+ Mpps.If you want your network core (6500's) with a high traffic should perform very well, you might thought of getting DFC;s for your modules.

DFC is eventually a PFC daughter card which is there on the sup engine. Once you have DFC enabled on the card, it will have all the layer2 and layer 3 tables downloaded locally on it and does the local re-writing of the packet without going to the PFC on the sup engine.The traffic between the ports on the same DFC enabled module will see a little improvement. The traffic between the DFC module and the other non dfc module will use the 32 gbps shared backplane for forwrading the traffic. When all the line cards are DFC enabled, they use Switch fabric (Integrated on Sup 720) to switch all the traffic and the 32 GBps shared bus doesnot come into the picture.That's why you see a very good optimization when you have DFC's on all the line cards.

http://www.cisco.com/en/US/products/hw/switches/ps708/products_qanda_item09186a0080159963.shtml

HTH,Please rate if it does.

-amit singh