NEXPEED NBG440 User’s Manual
NexComm Systems, Inc. 80 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, NBG440 can perform a service known as Network Address Translation(NAT).
NAT works as follows: When the local host sends packets to the remote network, NBG440
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, NBG440
automatically translates the official address on the remote network to the host’s private address on
the local network.
The router supports classic NAT (one NAT IP address assigned to one local IP address) and PAT
(one single NAT IP address assigned to many local IP addresses).
Note1:
To operate NAT/PAT feature, IP Routing mode must be enabled. To prevent the local
network address from propagating to the Internet or remote networks, turn RIP off.
Note2:
You can set NAT operation to only one of the interfaces on the router.
PAT (one single NAT IP address shared by many local IP addresses)
With PAT, multiple local IP addresses are mapped to a single global IP address. Many local IP
addresses are therfore hidden behind a single global IP address. The advantage of PAT is that users
only need one global IP address, but the entire local LAN can still access a public network such as
the Internet.
