Filter Traffic only

[rfrazier]

Is OPNsense able to be placed in between the ISP modem and an Internal Router to filter traffic only?  I thought that what transparent bridge filtering would do, but I'm not having much success.  ISP is connected to the WAN interface and Internal Router is connected to LAN, both interface has been added to bridge 0 which has been assigned a static ip of the local lan that I am trying to filter the traffic to.  I followed the documentation on https://docs.opnsense.org/manual/how-tos/transparent_bridge.html, but the more I go down the rabbit hole, it appears I'm doing this wrong.  How should I be configuring OPNsense to just filter traffic between the lan and wan.

[m-a-l@tuta.io]

Hello rfrazier,
have you found a solution for your topic?
I'd like to have the same scenario here, but have the same issues with it.

[Patrick M. Hausen]

This depends on the type of ISP modem and router and the method to establish the Internet connection. If the router talks PPPoE to the upstream network, you are out of luck. OPNsense cannot look inside the PPPoE stream.

If the "modem" is in fact an Ethernet network endpoint and the ISP router gets its IP address via DHCP, then you can put OPNsense between them as a transparent filtering bridge as described in the documentation.

But why not filter behind the ISP router? If you don't trust the ISP that makes much more sense, IMHO.