Learn firewall, NAT, routing and gateways properly

[beneix]

I have used OPNSense for over five years now. I have gradually introduced more and more advanced configurations such as road warrior Wireguard access, OpenVPN client, VLANs, various plugins, etc. All along, I have felt that I was behind the learning curve on really understanding the firewall rules, NAT, interfaces/aliases and gateways. I have somehow managed to get things working, but sometimes without understanding why. I find the interaction between these concepts particularly confusing.

Now I would like to address my knowledge deficit and learn these things properly before I attempt the long-delayed migration from legacy firewall rules. I would appreciate pointers to good learning resources that will help.

[bob9999]

I have always been under the impression that many posters here learn OPNsense and confuse that with learning networking. Hopefully you aren't making that mistake. If you learn basic networking concepts as if you were taking a survey course, you will much better understand what you are actually doing when you want to give your network a new feature.

With your network plans, first decide what objective you want to accomplish in a conceptual way without regard to OPNsense. Then figure out the generic way to do it, more or less. Finally, figure out how it's done in OPNsense.

Look up Intro To Networking courses on YouTube. Long ones in many parts that cover a lot of territory. Maybe even buy a cheap old used text book on it from Amazon. Basic networking hasn't changed a lot in over a decade. The basic stuff is what you want to learn so you can understand the newer and more exotic things later.

[Bob.Dig]

For some basic stuff in German, you can go here:
https://www.youtube.com/watch?v=HrUZjqqWPZM
But you probably don't speak German, I guess. ;)