Please note that in the above diagram, the Gateway IP address settings for the local PC’s needs to be set to 192.168.0.1, the LAN IP address of the router.
NAT manipulates the IP addresses in packet headers on a
In the Outgoing Data Packet above, the Source IP address is the IP address that is translated by NAT. The Destination IP Address is the IP address of a computer outside the private network, on the Internet for example. And the Data portion of the packet is the information payload carried by the packet, for instance a request to view a web page.
The router logs the changes made to the IP header in its NAT table. The NAT table enables the router to send replies back to the local computer as shown below.
In the Inbound Data Packet above, the Destination IP Address is the IP address that is translated by NAT. The Source IP Address is the IP address of a computer outside the private network. And the Data portion of the packet is the information payload carried by the packet, in this case, web page contents.
Setting Local IP Addresses
When implementing NAT and thus creating a private network that is isolated from the Internet, you can assign any IP addresses to host computers without problems. However, the Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of IP Addresses specifically for private networks:
Class | Beginning Address | Ending Address |
A | 10.0.0.0 | 10.255.255.255 |
B | 172.16.0.0 | 172.31.255.255 |
C | 192.168.0.0 | 192.168.255.255 |
It is recommended that you choose local IP addresses for use with NAT from the private network IP addresses in the above list. For more information on address assignment, refer to RFC 1597, Address Allocation for Private Internets and RFC 1466, Guidelines for Management of IP Address Space.
Port Redirection
17