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 ?

  • You're going to be busy for a long time just setting it all up. If it were me, though, I would use a separate NAT for each subnet.
    – SDsolar
    Mar 1, 2017 at 20:18

4 Answers 4


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).

  • 2
    NAT has nothing to do with security. Using NAT as a security feature is a terrible idea.
    – JFL
    Mar 11, 2017 at 16:49

Yes, it is. Subnetting is helpful for dividing a network into smaller networks. This is more efficient than traditional classful IP addressing. Data travels faster and more efficiently.

NAT (Network Address Translation)is a protocol that translates a private IP into a public IP. We use NAT when accessing the Internet. NAT is also useful for preserving the IPv4 lifespan, since Port address translation (PAT), can translate multiple private IPs into a single public IP.

  • PAT is a vendor-specific term for NAPT. See RFC 2663, IP Network Address Translator (NAT) Terminology and Considerations and others (just search for rfc napt): "NAPT extends the notion of translation one step further by also translating transport identifier (e.g., TCP and UDP port numbers, ICMP query identifiers). This allows the transport identifiers of a number of private hosts to be multiplexed into the transport identifiers of a single external address. NAPT allows a set of hosts to share a single external address."
    – Ron Maupin
    Dec 19, 2022 at 19:02

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