Firstly N300 is not the router model. If you look at the label stuck to the side/bottom you should find the model number. It'll most likely be something like DGxxxx.
Also, since you say that the unit has a DSL light, then it's probably a combination modem and router built into the same unit. For this you should really post in the RangeMax Next Routers forum. However, before you do that, you could perhaps help yourself by browsing to support.netgear.com and downloading the Manual for your unit. Have a look at the Troubleshooting Section and see what the behavior of the lights mean and what the recommended action is. If you still need help, then start a new thread in the appropriate forum.