A DFC is installed in DFC-enabled line-card modules to perform distributed forwarding supported by the Supervisor Engine. When the Distributed Forwarding Card is installed, line cards that are DFC-enabled make forwarding decisions locally, leaving the supervisor engine free to perform routing and management functions. This increases your overall performance and scalability. The Distributed Forwarding Card replicates Layer 2 and 3 forwarding logic in hardware as well as a bus on each line card as well.
For example, the 8-port 10GbE module WS-X6708-10G-3C has 40 Gbps connection to the fabric and can demonstrate up to 64 Gbps local switching. The distributed forwarding card (DFC) can forward traffic at 48 Mpps enhancing the module’s speed and performance.
Often, these are field upgradeable.