1-to-1 Network Address Translation: How to Use It Effectively
Introduction to 1-to-1 network address translation ( static NAT)
Network address translation plays a crucial role in conserving IPv4 addresses. One of the main and most commonly used of NAT is 1-to-1 network address translation. We can also call it static NAT. This article will explore its details, configuration, use cases, and practical implementation. At last, you will find a solid understanding of how to implement 1-to-1 NAT in a real-world scenario.
What is 1-to-1 NAT?
It is a type of NAt, where each local PC in a LAN maps its private IP address to a unique external public IP address. This type of NAT enables a PC in a LAN to communicate over the internet. Unlike other types of NAT, such as dynamic NAT and PAt, 1-to-NAT doesn’t change its public IP address. Its public IP address remains permanent, providing consistent communication between the internal and external networks.
Why Use 1-to-1 NAT?
We use 1-to-1 NAt in a scenario where a local device needs access to the internet over a consistent public IP address. Some common use cases include which are:
- Hosting Services: You can’t assign a dynamic IP address to the servers when it needs to be accessible to the internet. For this, we use 1-to-1 NAt, which ensures that the server has a consistent public IP address.
- Security: It helps in hiding the private address from the outside world.
- Compliance: sometimes it is the requirement of regulatory authority that specific devices must have static public IP addresses for audit and tracking purposes.
Implementation of 1-to-1 NAT
We will use the following lab topology for our 1-to-1 static NAT mapping. There are four routers, in which R1 has a LAN and the PCs in R1 need to access the HTTP server in R4’s LAN.
- Configure basic IP addresses on all routers, servers,s, and PCs in the diagram
- Run an EIGRP routing protocol on R2, R3 and R4.
After configuring IP addresses and running routing protocols on R2, R3, and R4. The next step is to define default-route on R1.
R1(config)# ip route 0.0.0.0 0.0.0.0 1.1.1.2
Ping all the routers and HTTP servers from router R1.
Also, ping R2 and HTTP server from PC1.
The router R1 doesn’t allow PC1 to access the HTTP server on the internet. To access the server from PC1, we will configure static nat on R1.
Configure static NAT or 1-to-1 NAT on R1 and then configure inside and outside NAT interfaces on the same router.
Now check the ping from PC1 to the server.
Browse the HTTP server in the PC’s browser.
But you will not be allowed to browse the server from PC2 because we didn’t allow him to access the internet. Let’s check it.
Now will also configure static NAT for it, to access the server. As we have assigned 1.1.1.1/8 to the PC1, so we will use 1.1.1.3 to the PC2 in static or 1-to-1 network address translation.
Now browse the same server from PC2;
Also, ping the server from PC2.
Till now, we either ping or browse the http server from the R’s LAN. Now, we will ping R1 LAN’s PC1 from the server through the public IP (1.1.1.3/8). The IP address 1.1.1.3 is not the address of any interface, but it is the public IP of PC2, which was mapped with it through static mapping.
NAT Translation Table
You can check the translation table through the command “show ip nat translation”. It will verify whether the NAT configuration is working or not.
How to check NAT Translation Traffic
If you want that how the router translates private IP address to the public IP address, then you can check through the ‘debug ip nat’ command:
