OpenWrt device with port mirroring enabled to act as if it is between the opnsense device and the ISP device
Internet
|
[ ISP device ]
| (WAN link)
| eth0
|
+------------------------+
| OpenWrt switch/hw |
| (port-mirroring on) |
| |
| Port A <-----> Port B|
| (to ISP) (to OPNsense WAN)
| \ |
| \ |
| \ |
| [mirror] |
| | |
| Port M (monitor) <-+ <-- capture machine (tcpdump/wireshark)
+------------------------+
ISP modem --- port 1 (switch) ---+
\
\ (traffic flows between port1<->port2)
+--- port 2 (switch) --- OPNsense WAN
|
+--- port 8 (switch, monitor) --- Capture PC (eth0)
(port 1 or port 2 mirrored => port 8)