By default, switches or L2 devices create separate collision domains however maintain a single broadcast domain. Each interface in a Switch is its own collision domain. A Layer 1 device or Hub, maintain one collision and one broadcast domain. In the exhibit, the LAN with Hubs would be one collision domain, but if a switch replaces each Hub, the collision domains would be broken into each number of interfaces that each Switch has. L2 or Ethernet Broadcast would still be one, until a router is installed. Refer to [http://www.diffen.com/difference/HubvsSwitch].