What is the primary function of a router in networking?

The primary function of a router in networking is to connect different networks and route traffic between them. Routers are essential devices that analyze incoming data packets and determine the most efficient path for them to reach their destination across multiple networks. When a data packet arrives at a router, it checks the destination IP address and consults its routing table, which contains information on where to send the packet next. This process allows for data to be efficiently transmitted between diverse networks, such as connecting a home network to the internet or linking different organizational networks.

In contrast, the other options focus on functionalities that do not represent the main role of a router. For example, switching data within a local network pertains more to switches, which operate at Layer 2 (Data Link layer) of the OSI model, rather than the routing function. Providing a physical layer connection refers to the hardware aspect of networking, such as cables and connectors, which is not specific to routing. Encrypting data for secure transmission involves securing data, typically associated with firewalls and VPNs, rather than routing the traffic itself. Thus, the correct answer reflects the unique and critical role of routers in inter-network communications.