Netgear M4300-28G (GSM4328S) - Stackable Managed Switch with 24x1G and 4x10G including 2x10GBASE-T and 2xSFP+ Layer 3 管理者ガイド

Select Monitoring > Mirroring > Port Mirroring. 

A screen similar to the following displays.

Next to Admin Mode field, select the True radio button.

From the Destination Port menu, select 1/0/3.

Scroll down and select the check box to the left of interface 1/0/2.

1/0/2 displays in the Interface field of the table heading.

Click the Apply button.

Your settings are saved.

Mirroring lets you monitor traffic to and from a port by copying the traffic to a probe port for 
analysis. Mirroring is usually limited to on one switch. With a remote switched port analyzer 
(RSPAN), you can extend mirroring to all participating switches.