I'm unsure what my DNS is set to and can't check since my ISP blocks me from my router for some stupid reason.
as far as I know your router has little to do with it, aside from suggesting DNS servers (which the ISP suggests) to connected machines. you can check in your operating system's settings
on windows (10, but I think it's the same on any after 7), that's Control Panel > Network and Internet > Network Connections, then double click the adapter you're using, click "Properties" at the bottom, then double click the IPv4 thing in the list
should look like this:
as you can imagine, the bit at the bottom lists your DNS servers
