Cisco Certified Network Associate (CCNA) Practice Exam

The device that connects internal networks to external networks in a leased line scenario is a router. A router plays a crucial role in network connectivity by directing data packets between different networks. In a leased line setup, the router is responsible for interfacing the internal private network with an external service provider network. This allows for continuous communication and efficient data transfer across the leased line.

The router utilizes routing protocols to determine optimal paths for data transmission and ensures that data reaches its intended destination outside the internal network. It fulfills the function of managing IP addressing and can also provide features like Network Address Translation (NAT) and firewall capabilities, contributing to both connectivity and security.

In contrast, while other devices such as switches, hubs, and CSU/DSUs play important roles in network operations, they do not serve the primary function of connecting internal and external networks. Switches work within a local area network (LAN) to connect devices and manage traffic between them, but they do not handle external network communications. Hubs are even more basic, typically functioning as simple broadcast devices that connect multiple Ethernet devices within the same network segment without managing traffic intelligently. CSU/DSU devices are used to connect digital data lines to routers and serve as a bridge between the router and the leased