Abstract: A network switch has a plurality of mirror ports to which data is copied for purposes such as networking monitoring. Data flows are identified and copied to an appropriate mirror port in response to the type of flow, a mirroring policy set up by a network administrator, and a distribution mechanism. A monitoring device attached to each mirror port is able to monitor specific types of traffic. Because the data flows are distributed among a plurality of mirror ports and monitoring devices, the ports and devices are less likely to overflow and therefore are more likely to be able handle the copied data without dropping data packets. The mirror ports are collected into groups of such ports. A given port may only be a member of a single group at one time. The mirroring policy must identify the group to which a particular type of flow is copied.