Which network device is responsible for segmenting broadcast domains?

The device that is responsible for segmenting broadcast domains in a network is the router. Routers perform this function by creating separate broadcast domains for different network segments or subnets. When a device on one subnet sends a broadcast message, the router does not forward this message to other subnets. This means that routers effectively control traffic between different networks, enhancing overall performance and security by minimizing unnecessary broadcast traffic.

In contrast, hubs and switches operate at the data link layer and primarily deal with MAC addresses and frames rather than managing broadcast domains. Hubs transmit broadcast messages to all devices on the network without any filtering, while switches, although more intelligent than hubs, still keep all devices in a single broadcast domain unless configured with VLANs. Modems, on the other hand, are used to connect a network to the internet and do not segment broadcast domains, as they primarily convert digital signals into analog for transmission over communication lines.

Thus, a router is the correct choice for segmenting broadcast domains.