@TheNewbie92 You need to start by configuring one Deco as the main Deco. I believe you must configure it as Access Point, given how you are cabling your devices. Then you will add the other two Deco...

@Johan_E If your camera is statically setup to work with the old cable router, you might have to adapt the configuration of the Deco for the camera to continue working. Do you know the LAN IP used by...

@Mahbub Are the Deco configured as Router or AP? Is there are direct or indirect connection between the two Deco, can one Deco access Internet via the other Deco?

@Mahbub Your two Deco M9 are configured as independent Deco networks, both being main Deco in their own network?

@MLO0815 What do you change in the Deco to structure them as a line?

@LVDX What is your setting for IPv4? Did you try "dynamic IP" for IPv6? What are you trying to improve? Are your devices working on IPV6?