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 borne 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 borne by the packet, for example, the contents of a web page.
The actual information in the NAT table depends whether the router is implementing NAT or NAPT.
It is also of interest to note that this translation process provides a level of security to your network found in a firewall. If you examine the outbound and inbound packets above closely, you can see that the computer outside of the network that is receiving the packet and sending the response only knows about the global IP address used by the router, and actually sends the response to that address. The outside
Configuration and Management | 79 |
