Eicon Networks 1550 - Manual (Page 56)

Security 56
Network Address Translation (NAT)
The Eicon 1550/1551 uses network address translation (NAT) to ‘hide’ the local LAN
from all external resources. The benefits of this are the ability for all connected
computers to access the external network using one user account, defined on the
device itself. For example, when communicating with the external network, the four
computers in the following diagram share the IP address ‘222.182.22.39’.
Notes
• NAT operates transparently, translating internal addresses to a single external one
for all data traffic. NAT has no effect on total throughput.
• Most applications will work with NAT. However, some programs may not work well or
at all with NAT enabled.
• NAT is disabled by default.
Security benefits
An additional benefit of NAT is increased network security. Like a firewall, NAT restricts
access to the computers that reside on the local LAN; no computer on the internal LAN
is visible to the external network. Computers on the internal network cannot act as
FTP or web servers, nor can they share their drives using Windows Network
Neighborhood. These security features can be weakened if you use NAT static
mappings (see
NAT static mappings below).
NAT static mappings
With NAT enabled, computers outside of the internal LAN do not have access (are not
visible) to any computers on the internal LAN. If you need a computer on the internal
LAN to be visible to the external network, the Eicon 1550/1551 provides a solution
through NAT static mappings.
NAT static mappings allow you to permit specific computers on the internal LAN to
receive certain incoming network traffic. For example, you could designate a computer
to receive all incoming HTTP traffic, allowing it to function as a web server. However,
the actual IP address of this computer is still hidden by NAT. Therefore, remote users
must specify the address of the Eicon 1550/1551 to gain access to the web server.
IP Address
External
Network
192.168.1.1
192.168.1.5 192.168.1.4 192.168.1.3 192.168.1.2
222.182.22.39
HUB
LAN interface
Eicon 1550/1551