NAT can be performed both statically and dynamically. We want traffic hitting our router’s public IP 20.20.20.1 on port 80 to be redirected to our internal Web Server at IP 192.168.1.10
![cisco router configuration tool cisco router configuration tool](https://www.cisco.com/c/dam/en/us/support/docs/cloud-systems-management/router-security-device-manager/71305-basic-router-config-sdm-1.gif)
Static Port Address Translation (Port Redirection)Īssume now that we have only one public IP address which is the one configured on the outside interface of our border router. Ip nat inside source list 1 interface FastEthernet0/0 overload 2. This type of NAT is very useful in situations where our ISP has assigned us only a single public IP address, as shown on the diagram below.Īll IP addresses of the LAN network (192.168.1.0/24) will be translated using the public IP of the router (20.20.20.1).Īccess-list 1 permit 192.168.1.0 0.0.0.255 This type of NAT allows a maximum of 65,536 internal connections to be translated into a single public IP. It uses the concept of “ many-to-one” translation where multiple connections from different internal hosts are “ multiplexed” into a single registered (public) IP address using different source port numbers. This is the most frequently used form of NAT in IP networks. Overloading or Port Address Translation (PAT) NAT has many forms and can work in several ways, but in this post I will explain the most important types of NAT.įor the next 2 scenarios we will be using the following simple network:ġ.
![cisco router configuration tool cisco router configuration tool](https://www.cisco.com/c/dam/en/us/support/docs/cloud-systems-management/configuration-professional/111999-basic-router-config-ccp-39.gif)
The purpose of this NAT device is to translate the source IP addresses of the internal network hosts into public routable IP addresses in order to communicate with the Internet. Network Address Translation (NAT) therefore was introduced to overcome these addressing problems that occurred with the rapid expansion of the Internet.Įven if NAT was suggested as a temporary solution, it has been adopted by all network hardware manufacturers, and it is considered a very useful technology, not only for IP address conservation, but also for many other purposes including security.īasically NAT allows a single network device (e.g a router, firewall etc) to act as an agent between a private local area network and a public network such as the Internet. The depletion of the public IPv4 address space has forced the internet community to think about alternative ways of addressing networked hosts.