Mirrored port & duplicated response

[Tamadite]

In order to get acquainted with the virtues of OPNsense I have set it up to monitor the network only that is, OPNsense is not intervening the network traffic on my LAN.

For this I am mirroring port-1 on the switch onto port-7 which is connected to igb3 on my OPNsense. igb3 is configured in promiscuous mode. For management purposes I have set igb1 on the LAN (port-8).



The problem I encounter is that OPNsense ports igb3 and igb1 are both responding to traffic requests to igb1 which has IP 192.168.1.25, in other words, I would get double ping response when pinging 192.168.1.25 IP on the OPNsense, OPNsense web portal timeouts, etc.

What am I missing or doing wrong here?