If you have your network setup properly in which your IP cameras are hooked up to a seperate switch so the idle traffic stays off your router, you can have hundreds of cameras and it wouldnt affect your network given that you have quality switches with gigabit uplinks. The only time your "networK' would experience any kind of traffic from your IP camera system would be if a device such as a computer or cell phone requests information from that system for remote viewing purposes, then the combined bandwidth from the total amount of cameras that you are viewing at one time would be sent through that router.