if i have an organization and say i need about 25 Networks and 500 Hosts , well i'm going to use IPsubnet with CIDR To configure my ip addresses , what is the point of using NAT here ? , is it even possible to use NAT while i do have separate Subnet masks ?
Is it even possible to use NAT while i do have separate Subnet masks ?
-> Yes. As long as you have a route to the host in difference subnet, it's possible.
What is the point of using NAT here ?
NAT is used to hide the real IP of the host that connect to the outside, this is secure purpose of NAT. Another benefit of using NAT is saving the global IPv4 Address and providing a lot of internal IP address without any extra cost.
There are various reasons for using NAT but the big one is to allow you to use private IP addresess on your internal network while using a smaller number of public IPs (maybe only one) to talk to the Internet.
Whether or not your internal network is carved up into subnets is orthogonal to whether you use NAT at the gateway between your network and other networks.
From a purely networking point of view, if you have the available subnets you can just go ahead and use a normal IP addressing scheme.
However for network security purposes, NAT is recommended. It will also save on address space if their is room for network expansion in the future.
Bear in mind any servers/clients that need to be accessed externally will have to be put in some sort of DMZ or assigned a specific public address, as opposed to using PAT(NAT Overload, most commonly used).