3.4.4: Hosts on a single local network connected to a hub create a single collision domain. A switch increases the number of collision domains because it filters and forwards frames based on the source and destination MAC. However, switches still forward all frames with FFFF.FFFF.FFFF as the destination MAC address because it is a broadcast frame. When bandwidth needs or host numbers increase, broadcast traffic begins to slow a network. Routers do not forward broadcast frames; routers divide broadcast domains.