Understanding Port Mirroring

The port mirroring feature is used to gain visibility into the traffic flowing through the network, which assists in troubleshooting connectivity issues and monitoring the performance of network devices. Port mirroring  copies traffic from specific ports on a switch to other ports on the same switch or a different switch. To analyze the traffic, you must configure a destination port for the mirrored traffic where network analyzer tools can be connected. Consider the use case of an application that needs access to data flowing through the switch, but does not want to impede the flow. The port mirroring feature can provide the configuration required by this application.

NetVisor OS supports three distinct port mirroring functionalities:

Local Switched Port Analyzer (SPAN) mode: The simplest port mirroring configuration which copies traffic from one or more source ports to one or more destination ports on the same switch.

Remote Switched Port Analyzer (RSPAN) mode:  An extension of SPAN which copies packets between different switches by using a special user-specified VLAN to carry the traffic. This feature enables remote monitoring of multiple switches.

Encapsulated Remote Switched Port Analyzer (ERSPAN) mode: This configuration transfers mirrored traffic over a routed network (over IP) with GRE encapsulation.