Draytek Vigor2830 Series User Manual page 107

a table to memorize this address/port-mapping relationship. When the public server response,
the incoming traffic, of course, is destined to the router's public IP address and the router will
do the inversion based on its table. Therefore, the internal host can communicate with external
host smoothly.
The benefit of the NAT includes:
Save cost on applying public IP address and apply efficient usage of IP address.
NAT allows the internal IP addresses of local hosts to be translated into one public IP
address, thus you can have only one IP address on behalf of the entire internal hosts.
Enhance security of the internal network by obscuring the IP address. There are
many attacks aiming victims based on the IP address. Since the attacker cannot be aware
of any private IP addresses, the NAT function can protect the internal network.
On NAT page, you will see the private IP address defined in RFC-1918. Usually we use the
192.168.1.0/24 subnet for the router. As stated before, the NAT facility can map one or
more IP addresses and/or service ports into different specified services. In other words, the
NAT function can be achieved by using port mapping methods.
Below shows the menu items for NAT.
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Vigor2830 Series User's Guide