I agree with pVC.
Just leave the Router deal with your ISP on PPPoE. Hopefully, your Router will be capable of being a DNS Server. All you need to do is configure the Amiga to use the Router as a Defualt Gateway to the Internet. The router will hand out IP addresses & handle DNS, rather than each connected computer having to be configured. It gets very complex on multi-platformed Networks.
Get things right & Install Samba to get access to your Pee Cee files directly from your Amiga & vice-versa.
How to set up SambaGood luck! :-)