Best way to monitor a door from two angles

[Johnny1337]

Hi,

I have 2 cameras pointed to my front door, one from the left side and one from the right side of the door. What I would like is both cameras to record when motion is detected in one of them. If I link both monitors to each other, then there will be a loop?

How to solve it in best way? With 4 streams, 2 of each camera?

Thanks in advance!