Monitor everything that goes through my router-modem

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Problem :

I have spent days on google searching for what I need. I have found lot of forums but it has been difficult to understand them cuz of technical terms or abbreviations used.
I am not technie so please help me understand in simple words or lehman language how I can achieve what I need.

I have a Encore(ENHWI-2AN3) Wifi Router connected to cable modem (DOCSIS).
We connect couple of laptops, smart phone and tablets to this wifi.
I wanted to capture all the data(websites browsed, email content, facebook, whatsapp messages) that goes through the router.

How can I achieve it? I have heard getting tcpdump, using wireshark to read it but I never understood how to configure it.

Any help would be greatly appreicated.


Solution :

If you have a router behind a modem this is quite easy.

Some routers (like the FRITZ!Box) offer a web page where you can start a network capture. You will then get a file that you can open in Wireshark.

If your router does not implement such a feature, there is a second possibility. You can put a network switch between the router and the modem. If the switch allows mirroring one port to another, you can for example connect router to port 1, modem to port 2, a new dedicated capture PC to port 3 and set the switch to mirror all traffic on port 2 to port 3. Then the PC will see all network traffic. That PC should only be used for monitoring, not for sending any data. In case you have old technology around you can also use a network hub. (Dumb) Network hubs always send all data to every port, whereas (intelligent) switches only send data to the port where the receiver of the packet is connected.

Of course you can also take a PC with two network cards, connect the router to one network card, the modem to the other and configure the PC to bridge both network cards. Then all traffic from one card is transparently forwarded to the other and the PC can inspect any traffic.

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