Port mirroring copies all received and transmitted packets (including local traffic) from a source port to a predefined destination port, in addition to the normal destination port of the packets. Port mirroring, also known as sniffing, is useful in debugging network problems.

Port mirroring allows you to define a source port and a destination port, regardless of port type. For example, a 10 Mbps and a 100 Mbps port can form a valid source/destination pair. You cannot, however, define the port mirroring source and destination ports as the same source and destination ports.

You can define one source port and one destination port on each Branch Gateway for received (Rx), transmitted (Tx), or transmitted and received (both) traffic.