> Where do I download the software for R8000P [...]
If you mean the router firmware, then...
Visit http://netgear.com/support , put in your model number, and look for Downloads. (For older versions, under Firmware and Software Downloads, look for "View Previous Versions".) Find the kit(s). Download the kit(s) you want. Read the "Release Notes" file for instructions. (In the User Manual, look for "firmware", and, especially, for a topic like "Manually Upload Firmware to the Router".) When that fails because of a deficient User Manual, try:
