You can use various methods to monitor packets. One method uses physical hardware taps.
Network taps can be extremely useful in monitoring traffic because they provide direct inline access to data that flows through the network. In many cases, it is desirable for a third party to monitor the traffic between two points in the network. If the network between points A and B consists of a physical cable, a network tap might be the best way to accomplish this monitoring. The network tap has at least three ports: an A port, a B port, and a monitor port. A tap inserted between the A and B ports passes all traffic through unimpeded, but it also copies that same data to its monitor port, which could enable a third party to listen.
They can handle full-duplex data transmission
They are nonobtrusive and not detectable by the network with no physical or logical addressing
Some taps support full inline power with the capability to build a distributed tap
Whether you are trying to gain visibility into the server-to-server data communication at the edge or virtual edge of your network or to provide a copy of traffic to the Intrusion Prevention System (IPS) appliance at the Internet edge of your network, you can use network taps nearly anywhere in the environment. However, this deployment can add significant costs, operation complexities, and cabling challenges in a large-scale environment.