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Understanding Netopia NAT Behavior F-1
Appendix F
Understanding Netopia NAT Behavior
This appendix describes how Network Address Translation works within the Netopia R3100. The Netopia R3100 implements a powerful feature called Network Address Translation (NAT) as specified in RFC 1631. NAT is used for IP address conservation and for security purposes since there will only be a single IP “presence” on the WAN. This appendix describes the NAT functionality within the Netopia R3100 and provides examples for setup and use.
Network Configuration
Below is a diagram of the network referenced in this appendix.
ISP Network | Customer Site | ||
IP: 200.1.1.1 | Netopia Router | Netopia Router | |
WAN IP: 200.1.1.40 | LAN IP: 192.168.5.1 | ||
Mask: 255.255.255.0 | |||
Mask: 255.255.255.0 | Mask: 255.255.255.240 | ||
| |||
Router | MAC: | MAC: | |
|
| ||
| Netopia | ||
| Workstation A |
| |
| IP: 192.168.5.2 | LAN | |
Internet | Mask: 255.255.255.240 | ||
MAC: |
| ||
WWW Server | Workstation B |
| |
IP: 163.176.4.32 | IP: 192.168.5.3 |
| |
Mask: 255.255.255.0 | Mask: 255.255.255.240 |
| |
MAC: | MAC: |
|
Background
NAT is a mechanism employed within the Netopia R3100 to acquire a statically or dynamically assigned IP address on its WAN interface and proxy against locally assigned IP addresses on its LAN interface. The Netopia R3100 uses a
In order to fully understand how NAT works you must understand how a PPP connection is established and IP addresses are negotiated.