Dynamic NAT vs. Static NAT: Comparison and Differences

Network Address Translation (NAT) comprises three main types, with static NAT and dynamic NAT being two of them.

Static NAT is a form of address translation that establishes a permanent one-to-one mapping between an inside local IP address (private IP address) and an inside global IP address (public IP address). This mapping enables the private IP address to be accessible over the internet.

On the other hand, dynamic NAT is a type of NAT that creates a temporary mapping between an inside local IP address (private) and an inside global IP address (public IP address). This temporary mapping allows the private IP address to be routable over the internet for a specific duration.

In this post, we will discuss the differences between static NAT and dynamic NAT, giving you insights into their respective functionalities and use cases.

What is Static NAT?

Static NAT is a network address translation algorithm that maps private IP addresses to public IP addresses one-to-one based on the configuration of the network administrator. The mapping is permanent and does not change unless reconfigured by the network administrator.

What is dynamic NAT?

Dynamic NAT is a type of NAT that dynamically maps local IP addresses to global IP addresses on a temporary basis. This means that each time a device initiates communication with the internet, it is assigned a unique public IP address from the pool of available addresses (NAT Pool). This NAT pool is configured on the NAT-enabled router by the network administrator.

Dynamic NAT offers a flexible solution in environments where a large number of devices existing on the LAN need intermittent access to the internet. It optimizes the use of public IP addresses by allocating them only when necessary, offering a dynamic approach to network address translation, and also maximizing the use of available public IP addresses.

Static NAT Vs. Dynamic NAT: Key Differences

Here are key differences between Static NAT and Dynamic NAT;

1. Static NAT permanently assigns a public IP address to a private IP address, while dynamic NAT temporarily assigns a public IP address to a private IP address, releasing it once the communication session ends.
2. Network administrators manually configure a one-to-one mapping of IP addresses on static NAT, while dynamic NAT randomly maps the private IP addresses with a pool of IP addresses configured on the NAT-enabled router based on first-come, first-served.
3. Scalability: Dynamic NAT is more scalable because it can use the available public IP addresses to dynamically serve multiple private IP addresses that communicate intermittently over the internet.
4. Configuration Complexity: Static NAT is easier to configure. Static NAT just needs one-to-one mapping, while in dynamic NAT configuration, you need to create an access list and configure the NAT pool.
5. Cost: Static NAT is more costly because it needs one unique IP address for each of the private IP addresses on the local network.
6. Maintenance: Static NAT is easier to manage as configurations remain constant, while dynamic NAT requires periodic monitoring and management of address pools.

Dynamic NAT vs. Static NAT: Configuration

Dynamic NAT configuration is a bit more complex than static NAT configuration. In dynamic NAT configuration, you need to create an access list and NAT pool, while in static NAT, you just need to map the private IP to the public IP one-to-one.

Here are the commands to configure static NAT and dynamic NAT:

Dynamic NAT Configuration

The following Commands are used to configure Dynamic NAT for the network below;

R0>en
R0#conf t
R0(config)#access-list 1 permit 192.168.1.0 0.0.0.255
R0(config)#access-list 1 deny any
R0(config)#ip nat pool POOL_1 100.0.0.3 100.0.0.5 netmask 255.0.0.0
R0(config)#ip nat inside source list 1 pool POOL_1
R0(config)#int g0/0/1
R0(config-if)#ip nat inside
R0(config-if)#int g0/0/0
R0(config-if)#ip nat outside

Recommended: How to configure Dynamic NAT on cisco packet tracer

Static NAT Configuration

The following Commands are used to configure Static NAT for the network below;

R1>en
R1#conf t
R1(config)#ip nat inside source static 192.168.1.2 100.0.0.4
R1(config)#ip nat inside source static 192.168.1.3 100.0.0.5
R1(config)#int g0/0/0
R1(config-if)#ip nat inside
R1(config-if)#int g0/0/1
R1(config-if)#ip nat outside

Recommended: How to configure Static NAT on cisco packet tracer

Conclusion

The choice between static NAT and dynamic NAT depends on your specific application and the availability of the public IP address. Static NAT is suitable for networks where there are many available public IP addresses to map with private IP addresses, while dynamic NAT is more suitable when public IP addresses need to be managed.