Dynamic NAT

In our fast-paced world, the need for network management and security is a must in business or organization. Network Address Translation (NAT) is one of the core technologies used to control traffic from internal and external networks by managing IP addresses. Among the different NAT types, Dynamic NAT delivers more scalability and flexibility, while permitting internal private IP addresses to access public IP address servers when public addresses are directly maps one-to-one.

What is Dynamic NAT?

Dynamic NAT is used when you have multiple private IP addresses that need to be translated into to pool of public IP addresses. When Static NAT is used, a fixed internal IP address is always assigned to the same external public IP addresses, but Dynamic NAT allows only for a temporary 1:1 mapping of private and public IP addresses. Whenever anything inside the private network must communicate with the outside world, it is assigned a public IP address from a pool that is configured ahead of time and high enough so as not to cause any conflicts. Dynamic NAT is mostly used when a cloud has limited public IP addresses and multiple private devices want to communicate with outside networks or the internet. With Dynamic NAT, allocating the public IP addresses from a range of the pool allows home devices to take a public IP address when and only necessary, saving a limited number of resources.

How a Dynamic NAT Works

Implementation of Private-to-Public IP Mapping: When an internal device, for example, a computer/Server starts communication with the external network, like browsing a website or sending an email privately, private addresses assigned by NAT are hidden from the public so the device can only be reachable with private IP. This enables the internal device to communicate over the public network with a well-known, routable IP address.

Dynamic Mapping: The public IP address linked to an inside device is only held for the length of the session. When the communication session is completed, it will release the mapping between incoming public IP and outgoing private IP (port) into the pool so other devices can use that public IP. This temporary assignment helps to use public IPs most effectively, so that they are not reserved for longer than needed.

NAT can establish bidirectional communication, which means when a NAT device translates a private IP address into a public one, it also ensures that when the NAT receives a response from an external network, it modifies the destination IP back to the source. This bidirectional communication results in a seamless data transfer between internal and external networks.

As soon as an internal device creates a new session, the NAT device can assign another public IP from its pool using this Dynamic Reassignment mechanism to route the packet. This means the same internal device can be mapped to a different public IP based on availability.

Example of Dynamic NAT

Imagine your organization has a private network of IP addresses range of 192.168.1.0/24 where several devices — like computers and printers — need to have access to the internet from predefined ports only. The Company only owns 203.0.113.1 to 203.0.113.5 as public IP addresses.

In Dynamic NAT, when the computer with private IP address 192.168.1.10 browses the web, it would get assigned public IP address 203.0.113.2 only for this one connection! This mapping is valid for as long as the session exists and after the session dies, the public IP address goes back to the pool.

If there are multiple devices connected to the internet at one time, then NAT will dynamically provide public IP addresses to each available device. When an exit is detected, the address will be released. And when all public IP addresses in this pool are being used, any new devices trying to go out to the internet will have to wait until an address is released.

Benefits of Dynamic NAT

1. Optimal Assignment and Utilization of Public Ips

Dynamic NAT is beneficial in that it can make good use of a small group of public IP addresses. Dynamic NAT only assigns public IP addresses when there are requests, preventing the waste of an IP address. This is particularly in the case of an IPv4, where public addresses should be private!

2. Enhanced Security

Dynamic NAT helps secure your internal network by not directly exposing internal private IP addresses on the external network. Since external systems do not know internal IP addresses, attackers will have a hard time directly pinpointing devices.

3. Flexibility in Network Design

Network administrators have more flexibility, as many internal devices can be given access to the internet using a smaller number of public IP addresses. This is valuable for businesses or other organizations that have many internal devices and a scarce number of public IP addresses.

4. Cost Savings

When Dynamic NAT is used, especially when using IPv4, you could also save some money, since purchasing additional public IP addresses is expensive. Many businesses use a limited number of Public IPs due to the Dynamic NAT feature that allows more users to be on the internet with fewer public IPs.

5. Improved Scalability

Dynamic NAT dynamically scales your network by enabling more internal devices to easily communicate outside the local network, instead of than having one-to-one mapping public addresses. That kind of scalability is important for any business that plans to grow its networks.

Seasoned eMazzanti professionals can give you guidance concerning Dynamic NAT and other digital tools and solutions.