|Most all in one routers use rj11 as input and the (usually 4) output/lan ports use rj45.|
Is your router "just" a router - no built-in modem?
What make and model is your router?
Do you have a separate modem connected to your isp service? If so what make and model?
Most isp provide either an all in one router (has the modem and router in one), or sometimes just a modem with (usually) an rj45 output, with an rj11 as the service input/connection.
Most all in one routers use rj11 as input and the (usually 4) output/lan ports use rj45.
So what do you have - makes and models?