A router allows communication across separate broadcast domains. A broadcast domain is group of hosts and network devices in which a broadcast frame sent by one host can be received by all of the other hosts in the broadcast domain. A router determines the path to other destination networks, and forwards data packets to the next hop along this path. A router operates at Layer 3 of the Open System Interconnect (OSI) layered communication model and uses an Internet Protocol (IP) address hierarchy to identify and route data through source and destination devices.

A switch does not allow communication across separate broadcast domains. A switch creates collision domains and enables communications across different collision domains. A collision domain is a logical group of hosts and network devices where packets can potentially collide with one another, causing a communications disruption. Switches forward broadcasts so they do not form a separate broadcast domain unless Virtual LANs (VLANs) are created.

A hub does not allow communication across separate broadcast domains. A hub transmits frames, which means that they neither form separate collision or broadcast domains nor allow communication across these domains. Hubs are multiport devices that allow consolidation of various LAN segments and amplify signals that pass through them. Hubs operate at OSI Layer 1.

An access point does not allow communication across separate broadcast domains. Access points (APs) are OSI Layer 2 wireless hubs that allow client hosts to connect to the backbone network wirelessly.