User Manual

Version 3.03 SPEEDLAN 9000 Series Installation and Operation User Guide
3-54 General Functions of the Configurator
Three Features of NAT
NAT Background Info
Network Address Translation (NAT) occurs when there is a translation from one IP
address to another. There are several implementations of NAT - each with their own
purpose. One would choose the type of NAT that suits the task.
The SPEEDLAN 9000 offers 3 features that use NAT: Address Sharing, Internal Servers
and 1:1 NAT. Each is described below.
1. Address Sharing: This feature allows an administrator to share a public IP address
with privately addressed nodes. Typically, this is used to allow outbound connections to
the Internet from hosts who do not have IP addresses that can be reached from the
Internet. In implementing Address Sharing, requests to the Internet would be directed
to the SPEEDLAN 9000. The SPEEDLAN 9000 would then translate the source address
and port to one of its own, and then forward the request on to its destination. The
destination server would return the request to the SPEEDLAN 9000, which would
consult its NAT table, determine which host made the request, change the destination
address and port, and return the completed request. Similar to Internal Servers, this
process also creates the Network Address and Port Translations (NAPT). Address
sharing is possible when units need to act only as clients and do not need to respond to
requests. This is a useful feature if you have a limited number of public IP addresses.
You can use this feature to connect the whole LAN to the Internet using just one public
IP address. Here are some other benefits of address sharing:
• reduce costs by using only one Internet account.
• protect your information by hiding your workstations IP addresses.
• restrict those users you want to access Internet services and resources.
The main Address Sharing page allows you to share the IP addresses assigned to the
SPEEDLAN 9000's network interfaces with all nodes connected to a different network
interface.