I installed everything as outlined in the instructions. We'll call my main wi-fi BOB, and the extended wi-fi BOB_EXT. Both wi-fi networks work -- they have access to the internet.
However, BOB_EXT isn't really extending the BOB wi-fi. Laptops/iPhones that are connected to BOB_EXT can not see printers or other shared network devices that are visible on BOB.
Which router is connected to your WN3000RP? If on a NETGEAR router, when you log into your router and go to Advanced < Set up < Wireless Setup please make sure "Enable Wireless Isolation" is NOT checked.
Is your printer connected via usb or via IP address? If using a usb printer, is the printer and the connected computer both turned on? If using a usb printer, please Add the device to each computer on the network.
You can also try adjusting your firewall settings and turn on/off settings on your antivirus program.
