Which Cisco IOS command disables CEF on a specific interface?

The command that disables CEF (Cisco Express Forwarding) on a specific interface is "no ip route-cache cef". When this command is issued on an interface, it effectively informs the router to stop using CEF for packet forwarding on that interface, reverting to process switching instead. The "no" prefix in the command indicates that you are negating an existing feature—in this case, CEF caching.

CEF is designed to improve routing efficiency and performance by creating a forwarding information base (FIB) and an adjacency table that allow for rapid packet forwarding without the need to consult the routing table for every packet. However, there may be scenarios, such as troubleshooting or specific configurations, where you might want to disable it temporarily on an interface.

The other options do not accurately represent the syntax or the function necessary to disable CEF on an interface. It is important to use the correct command structure to ensure proper configuration and functionality within Cisco IOS.