Which network device operates primarily to separate collision domains?

A switch operates primarily to separate collision domains within a network. When devices are connected to a switch, each connection creates its own dedicated collision domain, which helps to minimize data packet collisions when multiple devices transmit data simultaneously.

In a situation where many devices are connected to a hub, they all share the same collision domain, leading to frequent collisions and network inefficiencies. A switch alleviates this issue by intelligently directing data to the appropriate device, maintaining separate domains and allowing for simultaneous data transmission between devices without interference.

While both bridges and routers also help in managing network traffic and can create separate collision domains, switches are specifically designed with this functionality in mind and are more effective in modern networking environments. As such, a switch is the most suitable answer for the question regarding the separation of collision domains.