Insecure way is to go into the router and Port Forward the ports on the camera so that you can see them from anywhere, but it opens your entire network up to hacking (but that has already been done by virtue of allowing the cameras access to the internet with P2P and UPnP.
The more secure way is to OpenVPN back into your network.
Many camera networks are unsecure, even those installed by professionals. This guide gives basic instruction in how to secure a camera network from the most common types of attacks. Perhaps the most important rule of securing a computer network is to not forward ports to unsecure services...
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