Using DHCP is not enough. I use 8 cameras that are Wanscam equivalents to secure my house. You need to connect to them individually and alter the port they use to display their video, (make sure they are different). Then you port forward the different ports to the appropriate IP Address.
You will find a nice system to monitor/control them as single web page remotely at
Blue Iris. You'll also find a handy dandy little iPhone app called LiveCams Pro.