A device on one network can communicate with devices on another network via a

A network gateway is a device that joins two different networks, which may operate with different protocols, addressing schemes, or architectures. It forwards traffic between them, translating protocols or addresses when the two networks differ, so that a device on one network can reach devices on the other. Devices that merely move data within a single network never leave that network's own segment.

The question asks which device lets a device on one network reach devices on a different network. That cross-network role belongs specifically to a gateway, which sits at the network boundary and forwards or translates traffic between the two networks.

• Hub/Switch: forwards frames among ports within a single local network segment at the physical or data-link layer; it never bridges two distinct networks.

• Utility server: provides one administrative service, such as authentication, monitoring, or DHCP, to clients already on its own network; it does not by itself provide cross-network reachability.

• File server: stores and serves files to clients already connected within its own network; it also does not connect separate networks together.

Since only the gateway operates at the boundary between two different networks and enables communication across that boundary, the gateway is the device described in the question.