With our NVR and DVR you can add a DVR to the NVR under remote device. There are issues with that though. Some firmwares will let you add the DVR multiple times BUT some will not, so you can only port in one channel off DVR depending on firmware. It is a firmware issue that we have not the ability to support, or specifically make work the way you want.  The best solution is to get a hybrid DVR to use both analog and IP cameras on same DVR. I'm not writing that to sell you more equipment but to elevate frustration when something does not work as expected. Also you do not have full control of DVR through NVR which if you want to change settings can be a difficult to deal with. Searching for playback as well as total stored footage is greater on the hybrid DVR.