Jason Dion's Network+ Course Practice Test

Segmenting a broadcast domain requires a device that separates networks and routes between them. A router operates at the network layer and does not forward broadcast frames from one network into another by default, so each connected network has its own broadcast domain. In contrast, a switch or bridge handles traffic at the data-link layer and forwards broadcasts within the same Layer 2 network (unless VLANs are in play to create separate domains, but inter-VLAN routing is still done by a router). A hub simply repeats signals to all ports, extending the same broadcast domain to every device. So, the device that creates separate broadcast domains is the router.