What is Network Address Translation (NAT) in networking?

What is Network Address Translation?

Network Address Translation (NAT) saves IP addresses by allowing private IP networks to connect using unregistered IP addresses. Before forwarding packets between networks, NAT converts secret internal network addresses into legal, globally unique addresses.

As part of this feature, NAT settings can reveal only one IP address for a whole network to the outside world, essentially masking the entire internal network and giving additional security. Network address translation is commonly used in remote-access scenarios because it provides both address conservation and better security.

How does Network Address Translation work?

A NAT operates by selecting gateways that connect two local networks: the internal network and the external network. Inside network systems are often issued IP addresses that cannot be forwarded to external networks (for example, networks in the block).

The gateway has few external valid IP addresses. The gateway disguises outbound traffic from an inside system as coming from one of the valid external addresses. Incoming traffic directed at a genuine external address is routed to the relevant internal system.

This contributes to security. Because each incoming or outgoing request must go through a translation process that allows for the qualification or authentication of incoming streams and matching them to outgoing requests, for example.

NAT reduces the number of globally valid IP addresses required by a corporation and, in conjunction with Classless Inter-Domain Routing (CIDR), has significantly extended the useful life of IPv4. In general, NAT is described in IETF RFC 1631.

What is the Purpose of NAT?

A networking system requires a unique IP address in order to communicate with the internet. This 32-bit number is used to identify and locate network devices so that users can communicate with them.

Although the IPV4 addressing technique of previous decades made billions of these unique addresses available, not all of them could be assigned to devices for communication. Instead, some were exempted and utilised for testing, broadcasting, and specific military uses. While this left over 3 billion addresses for communication, the development of the internet meant that the addresses were nearly depleted.

The IPv6 addressing system was introduced to solve this flaw in the IPv4 addressing method. IPv6 recreates the addressing system, allowing for more address allocation alternatives, however it has taken several years to change the networking system infrastructure and implement. In the meanwhile, Cisco introduced and widely used NAT.

What are the types of NAT?

NATs are classified into three categories. People employ them for various purposes, but they all function as NATs.

  • Static NAT
  • Dynamic Network Address Translation
  • PAT

Static NAT

When converting a local address to a public address, this NAT uses the same one. This means that the router or NAT device will have a consistent public IP address.

Dynamic Network Address Translation

Rather of using the same IP address each time, this NAT cycles over a pool of public IP addresses. As a result, each time the router translates a local address to a public address, the router receives a different address.


PAT is an abbreviation for port address translation. It’s a form of dynamic NAT, except it connects multiple local IP addresses to a single public one. PATs are used by organisations that desire all of their employees’ activity to use a single IP address, often under the oversight of a network administrator.

Network Address Translation Configuration

A standard NAT configuration necessitates at least one router interface (NAT outside), another router interface (NAT inside), and a set of rules for translating IP addresses in packet headers and perhaps payloads.

  • The ISP assigns a range of registered, unique IP addresses to the enterprise. Inside global addresses refer to the assigned list of addresses.
  • The team divides unregistered, private addresses into two groups: one tiny and one much larger. The stub domain will use the broader group of addresses known as inner local addresses. Outside local addresses will be used by NAT routers to convert the outside global addresses or unique IP addresses of devices on the public network.
  • The majority of stub domain computers connect with one another via inner local addresses. Inside global addresses are available for stub domain systems that connect significantly outside the network and do not require translation.
  • When a normal stub domain computer with an inner local address has to communicate outside the network, the packet is routed through a NAT router.
  • The NAT router looks up the target address in the routing database. If the NAT router has an entry for that address, it will translate the packet and record the activity in the address translation table. If the target address is not in the routing table, the packet is dropped by the NAT router.
  • A computer on the public network sends a packet to a machine on the private network. The destination address of the packet is an inner global address, and the source address is an outside global address.
  • By validating the address translation table, the NAT router ensures that the destination address corresponds to a stub domain computer.
  • After translating the packet’s inside global address to the inside local address, the NAT router transfers the packet to the destination computer.

NAT Router

A NAT router uses NAT overload to build a network of IP addresses for a local area network LAN and connects it to the public network known as the internet. The router performs NAT, which allows communication between the WAN or internet and the host devices or computers on the LAN network. Because NAT routers appear on the internet as a single host with a single IP address, they are commonly utilised in small-scale companies and at home.

Advantages and Disadvantages of NAT

Advantages of NAT

  • Reduces costs:- When a company utilises NAT with its private IP address, they do not need to purchase a new IP address for each of their machines. They can use the same IP address for several computers. This will help to lower the organization’s costs.
  • Conserving Addresses:- When you utilise NAT overload, you can conserve the IPv4 address space, giving you access to all privatised intranets. This is possible in this case thanks to Intranet Privatization. They used to save all of the addresses at the port level in numerous programmes during this operation.
  • Connection Flexibility:- NAT includes a number of tools, including load balancing and backup solutions. These tools will aid in increasing the network’s overall resilience and flexibility. It will occur whenever we establish any link, whether public or any of their connections.
  • Network Consistency:- It has a method known as consistent network addressing. It has a dedicated address space for the use of public IP addresses. This occurs because as the network grows, more IP addresses are necessary.
  • Network Security:- In-Network Address Translation will totally conceal all of your original source and destination sources. Without the user’s authorization, so that other hosts in the network cannot reach the hosts inside them. This demonstrates that they have greater security.
  • Private Addressing:- They have their own private IPv4 addressing scheme. So, even if you switch to a different addressing system, they will retain their existing addressing scheme. If the user switches internet service providers, the internal address changes will be prevented.

Disadvantages of NAT

  • Performance Issues:- For example, if a visitor makes a request to a distant server, it will first check and confirm whether or not the connection belongs to the NAT server. Furthermore, some servers used to use security procedures to limit the number of requests that might be received. If the number is exceeded, they will be unable to make any further requests. This will degrade performance in real-time protocols.
  • Application Use:- Hosts inside the network may become unavailable at times. As a result, some programmes in the NAT will be incompatible. This will be dependent on end-to-end capabilities, which certain networks will be unable to provide.
  • Protocol Usage:- While the values inside the headers can be altered in NAT, some tunnelling protocols, such as IPsec, will be extremely difficult to use. When you change the values inside the headers, integrity tests are performed, which interfere and fail them.
  • Use of Services:- When using NAT, services such as TCP or UDP will be required. These services will be impacted while in use, making them unstable. Incoming packets will also encounter certain difficulties as they attempt to reach their destination. We can solve this problem by setting them with a NAT router.
  • Memory Utilization:- NAT will analyse the data packets of incoming and outgoing services. They will also convert data packets into local and global IP addresses. The translation details will be saved in memory. This, in turn, will require a lot of memory and processor power.
  • Troubleshooting Problems:- End-to-end traceability is limited when NAT is used. Furthermore, the IP address will be altered repeatedly. As a result, troubleshooting will be more complex. It will be more difficult in some circumstances, especially if you are in a rural location.