Hi,you mention that you can ping some hosts in the Internet. What is not working then?You also mention that during flushing the ARP cache the internet does not work... How long does that actually take? Normally it should be an action of a few milliseconds.Maybe the issue is that your ISP router somehow glues the MAC address of your router? In that case you could fake the OPNsense's box's MAC address on the WAN port.BRManuel