You're applying for a fixed public IP address, and your ISP is asking you for details about your local network? Can't you configure the LAN settings through the router's web interface?
I don't know. I'll ask my ISP to confirm whether I can set the router myself after Holiday. If YES, I'll ask ISP to preset all items default.
I recalled at time on contacting ISP, they told me that they can remote access the router to set it preventing other workstations on my LAN downloading spam messages. They do know that I have only a server without LAN setup. This is only a test for me.
I tried to register a domain with "godaddy.com". They need my email address not with Yahoo, Google, etc. Therefore I have to setup my broadband connection first before I can proceed further.
Anyway, which IP addresses are you currently using in your LAN?
Sorry I don't follow. There is no LAN at present.
Merry X'mas and Happy New Year