How to analyze external network traffic with a "server in the middle"?

Question

Computer networks

It is urgent to somehow sniff all the traffic going to the modem from the local network. Offhand, the idea is as follows:
1) We stick a machine with two network adapters between the switch and the modem (in my case, running Win Server 2012r2)
2) We set up a "bridge" connection between two adapters
3) We put any sniffer and "listen" to the network bridge
Implement this need seamlessly and as transparently as possible for ordinary users.
All right? If not, please indicate your options. I have only one attempt to install "wiretapping".

Answer 1

What about mirroring? Do you have access to the switch?