Cannot reach internet from LAN interface in custom setup

[gianrathgeb]

Dear Community

I have a problem regarding my custom setup of OPNsense (you can find it as an attachment).
I cannot reach the internet from the LAN interface, but I can reach it from the WAN interface of the OPNsense firewall.
As you can see, my ISP router does perform all functions of a router and is not configured as a modem. Is it possible to configure the firewall that I can reach the internet from the LAN interface or do I have to reconfigure my ISP router to a modem?

 If you need more information, please contact me.

Thank you in a advance for a response.

[bartjsmit]

Configuring your router as a modem is the best solution. It saves having to manage two devices for each dataflow.

You can also set up your OPNsense in transparent mode, but that is a bit trickier. https://docs.opnsense.org/manual/how-tos/transparent_bridge.html

Quickest may be to fix your current setup. Does ping 8.8.8.8 work from the LAN? Are you seeing denies in the OPNsense firewall logs? Do you have RFC 1918 address ranges allowed on your OPNsense WAN interface? Does your ISP router have a static route to your LAN subnet?

Bart...

[verasense]

Yes, of course you can use OPNsesnse and reach the Internet from the LAN.

I suppose the problem is how you have configured OPNsense...

Even though it is not your specific situation, check if any of this can help:
https://forum.opnsense.org/index.php?topic=4794.0
https://www.reddit.com/r/OPNsenseFirewall/comments/p16ee0/route_lanopnsense_traffic_to_existing_router/

[gianrathgeb]

Thank you for the answers, I think both of them will help me.
I will try them out and come back if the connection still fails.