NEXPEED NR304G-4W User’s Manual
NexComm Systems, Inc. 57 PAGE
Configuring NAT
To connect to the Internet or any other TCP/IP network, a host must have an IP address that is
unique within that network. The Internet and other large TCP/IP networks guarantee the
uniqueness of addresses by creating central authorities that assign official IP addresses. However,
many local networks use private IP addresses that are unique only on the local network. To allow a
host with a private address to communicate with the Internet or another networks that requires an
official IP address, NR304G-4W can perform a service known as Network Address
Translation(NAT). NAT works as follows:
When the local host sends packets to the remote network, NR304G-4W automatically translates
the host’s private address on the local network to an official address on the remote network.
When the local host receives packets from the remote network, NR304G-4W automatically
translates the official address on the remote network to the host’s private address on the local
network.
The IP address conversion can be performed in the following three ways:
1> Static Mapping
The NR304G-4W establish a one-to-one mapping between the private IP and public IP.
This translation is used when the connection to the internal network is attempted from
the outside. It is often used for the server IP address application.
2> Dynamic Mapping
Usually, this method takes a dynamic n:n translation. The translations between the local
network and the Internet or remote network are dynamic.
3> Port Mapping
Usually, this method takes a dynamic n:n translation and not only the IP address but also
port number translation is performed. For outgoing calls, the NR304G-4W performs
NAT for multiple hosts on the local network after getting a single IP address from the
remote network. For incoming calls, the NR304G-4W can perform NAT for multiple
hosts on the local network by using the single IP address.
