ToughNet NAT Router User's Manual
Network Address Translation
6-2
Network Address Translation (NAT)
NAT Concept
NAT (Network Address Translation) is a common security function for changing the IP address during Ethernet
packet transmission. When the user wants to hide the internal IP address (LAN) from the external network
(WAN), the NAT function will translate the internal IP address to a specific IP address, or an internal IP address
range to one external IP address. The benefits of using NAT include:
•
Uses the N-1 or Port forwarding Nat function to hide the Internal IP address of a critical network or device
to increase the level of security of industrial network applications.
•
Uses the same private IP address for different, but identical, groups of Ethernet devices. For example,
1-to-1 NAT makes it easy to duplicate or extend identical production lines.
NOTE
The NAT function will check if incoming or outgoing packets match the policy. It starts by checking the packet
with the first policy (Index=1); if the packet matches this policy, the ToughNet NAT Router will translate the
address immediately and then start checking the next packet. If the packet does not match this policy, it will
check with the next policy.
NOTE
The maximum number of NAT policies for the ToughNet NAT Router is 128.
1-to-1 NAT
If the internal device and external device need to communicate with each other, choose 1-to-1 NAT, which
offers bi-directional communication (N-to-1 and Port forwarding are both single-directional communication
NAT functions).
1-to-1 NAT is usually used when you have a group of internal servers with private IP addresses that must
connect to the external network. You can use 1-to-1 NAT to map the internal servers to public IP addresses.
The IP address of the internal device will not change.
The figure below illustrates how a user could extend production lines, and use the same private IP addresses
of internal devices in each production line. The internal private IP addresses of these devices will map to
different public IP addresses. Configuring a group of devices for 1-to-1 NAT is easy and straightforward.
