Static Nat is highly useful in situations where we have to make our internal network accessible from the public network. For example, if have a web server we can statically map the server’s IP address with public IP address so that it can become accessible from the internet.

We can also make multiple static Nat entries if we want more devices to be accessible from the internet. Additionally, we can map the port numbers in a static Nat. So, if the request comes from the internet for a specific server then the traffic is forwarded to the port number, which is assigned in the static mapping. This way we can use one public IP with the multiple static entries.

For eg. We want to have web server that can be accessible from the internet so we will direct all traffic that is coming to the public IP on port 80 to the internal IP that is assigned to the web server. Now a days, almost every website is using https so we can also redirect traffic to the web server that is coming on the port 443. But, we cannot have another webserver if we are using only 1 public IP address because we have already configured one to one mapping for the traffic that is being sent to port 80 so to use another web server, we have to use another public IP address and configure one to one mapping with the IP address as well so that request coming from particular website should be routed properly to different webservers with in the network.

Static nat is not so common form of NAT used in the organization, most common form of NAT used is NAT with overload, which allow various devices to communication with the external network at once however as a network engineer, we must know the difference between various types of NAT and this can also be ca good interview question so if you are preparing for the job interview then you should know the difference between them.

In this lab, we will perform a basic Nat configuration and map private IP with the public IP address.

Static Nat is very simple to configure on a Cisco router. We have to label the interface with Nat inside and outside, and then map the private IP with public IP one to one.



Static NAT example


Lab Tasks

1. label the interfaces
2. Enable static NAT

Lab Configuration

Task 1

Router0(config)#interface fastethernet 0/0

Router0(config)#ip nat inside

Router0(config)#interface fastethernet 0/1

Router0(config)#ip nat outside

Task 2

Router(config)#ip nat inside source static