If you’re running your custom
homebuilt router, you can use IDS systems like snort[0] or suricata[1]
It’s pretty fun to setup !, you can take any old desktop/laptop at your home and make them into your own custom router by running a linux or bsd instance on it.
If you go this route, I would recommend suricata ids as you can setup more complex and sophisticated system easily, compared to snort.
[1](https://suricata.io/)