Sorry for the dumb question and hopefully this is relevant enough to the sub. I have my own firewall and right now it connects to my ISPs provided home router over rj45, their router gets a fiber hookup to their network and it’s the only ISP device in my home. If I have a firewall with a fiber port, can I take the fiber to the modem and hook that straight to my firewall, or is there a reason I need their device?
I guarantee your ISP’s router has some sort of Network Access Control (either Certificate or MAC addressed) based authentication that controls access to the ISP’s network. The ISP would be crazy to not do that.
It is an easy test. Just by-pass the router and see if it works.
The worse that can happen is your personal devices get denied access.
Some ISPs will also let you switch to your own modem if you call them and set it up with them. Have done that for years with my ISP as they otherwise charge a rental fee for their modem that pays for a completely brand new modem after only 6 months.
As others mentioned, it depends. Germany has freie Routerwahl by law and ISPs have to allow you using your own router. They won’t offer support configuring it if course but they usually provide you with some credentials to properly authenticate.
I was kind of expecting something like that. If I wanted to do the test, would I just set the wan side of my firewall to dynamic and see if it picks up an address?
Yeah the ISP will have to give you an address. The headache might be finding out DHCP server’s hostname. You may be able to find that out from the IP information on the ISP Issued router you have.