Port mirroring is the capability on a network switch to send a copy of network packets seen on a switch port to a network-monitoring device connected to another switch port. Port mirroring is also referred to as Switch Port Analyzer (SPAN) on Cisco switches. In VMware vSphere 5, a Distributed Switch provides a similar port mirroring capability that is available on a physical network switch. After a port mirror session is configured with a destination -a virtual machine, a vmknic or an uplink port-the Distributed Switch copies packets to the destination.