R8000P Static routing to ISP router for internet access.

Router is a L3 (Layer 3) device and its job is to offer data traffic from one network to another. If they can't do that than to me they shouldn't be classified as Router to begin with. 

Now to configuration part. If I have a subnetwork, it shouldn't be difficult to configure. Unfortunately, This problem is mainly associated with unmanaged routers. As NAT does the automatic Network translation and is restricted only to Class A, and Class B IP address scheme. That being said, the Class C IP address scheme is what used mostly for private networks and sub networks. This should be able to handled by having static routes with in the route.

Having sub-network is the way to Isolate the devices especially IoT (Internet of Things) devices. As they can easily get DOS attacks.  Thus preventing other networks and devices to get compromised.  And to communicate among the networks one need routers. 

In my particular case, the issue was that my ISP router didn't have the route as stated in previous replies. And guess what as soon as I include the Routes, The devices started working. 

Thank you all for your kind assistance and sharing wealth of knowledge.