I am still looking into it but my Asus router is setup as 192.168.21.xx and not the standard 192.168.1.xx
I found my MacBook is showing 192.168.1.3 but wouldn't using OpenVPN put it on my local IP of 192.168.21.xx
Honestly I am a little confused by these subnets. I'm not sure what you have set up on purpose and what might be an error. Is the NVR set up on a different network subnet as the rest of your network? (If so, that is something I address below).
That being said, there are there are three network subnets (more if you use VLANs) in play when you use a VPN and you need to understand how they relate and interact with each other......
First you have your local network. As I noted above I am a little unsure if it is set up as a 192.168.21.0/24 network or a 192.168.1.0/24 network, or both because you have set up a VLAN or are trying to keep your CCTV devices separate from the rest of the network. However if your local network has more than one subnet (which it would if you are using VLANs) you need to specify both/all subnets that you want to be able to access across the VPN. If you only entered 192.168.1.0/24 in this particular setting, then nothing on 192.168.21.0/24 would be available across the VPN, even if you can normally access it from the 1.0 network when you are on the local network. If you aren't intending to use two different network subnets on your local network, then it seems there might be some unresolved core network issues that need to be solved at the "local" level before you attempt to continue with the VPN.
Second you have the "tunnel" subnet. This is a network that is created by the VPN service for the sole purpose of connecting the two ends (local and remote) together. You should be able to enter the subnet you want to use for this "tunnel" as part of the VPN settings.
Third, you have the "remote" network that your device is on. It might be a cellular network, or a network at work, or another house, etc, etc, etc.
All three of these networks have to be on different subnets. You can control the first two subnets, but you really can't control the "remote" network subnet. For example, If you find yourself at someone's home that uses the same network subnet that you use at your home (192.168.1.0/24 for example), you will run into issues. Obviously 192.168.1.0/24 and 192.168.0.0/24 networks are the two most commonly used "default" networks on "residential grade" routers. Therefore it might be smart for you to choose a more random network subnet for your local network to prevent potential conflicts in the future when you find yourself on a residential network that has been set up on it's "default" settings.
