IP cameras require a network video recorder (NVR) or browser that will
communicate with each particular model of camera, which is proprietary
and unique. Each time you add an IP camera, you have to make sure that
the NVR supports that particular model. An NVR may also support only a
limited number of cameras from a particular manufacturer. Many IP
camera producers have a large variety of communication protocols.
Any analog camera can plug into any DVR. There are no compatibility issues when changing either the DVR or
any of the cameras. As a note, many DVRs today are hybrids wherein they
have seamless communication and management with both IP and analog
cameras on a common software interface.