What operation is performed by the data plane in a network device?

The data plane, also known as the forwarding plane, is responsible for the actual forwarding of user traffic. When a packet arrives, the data plane uses the information provided by the control plane (like the routing table or FIB) to determine the next hop and egress interface, then sends the packet out. Building a routing table from routing protocols is a function of the control plane, which determines the best paths. Performing FIB lookups for the egress interface is a more specific action within the data plane's forwarding process, but "forwards packets toward the next hop" is the overarching operation. Providing CLI access is a management plane function, used for device configuration and monitoring.