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Understanding Netopia NAT Behavior
Appendix C
Understanding Netopia NAT Behavior
The Netopia R5000 Series Router implements a powerful feature called 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 R5000 Series Router and provides examples for setup and use.
Network configuration
Below is a diagram of the network referenced in this appendix.
ISP Network
IP: 200.1.1.1
Mask: 255.255.255.0
Router
Internet
WWW Server
IP: 163.176.4.32
Mask: 255.255.255.0
MAC:
Customer Site | |||||||
Netopia Router | Netopia Router | ||||||
WAN IP: 200.1.1.40 | LAN IP: 192.168.5.1 | ||||||
Mask: 255.255.255.0 | Mask: 255.255.255.240 | ||||||
MAC: | MAC: | ||||||
Workstation A | Netopia |
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IP: 192.168.5.2 |
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Mask: 255.255.255.240 |
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Workstation B |
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IP: 192.168.5.3 |
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Mask: 255.255.255.240 |
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Background
NAT is a mechanism employed within the Netopia R5000 Series Router 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 R5000 Series Router uses a
In order to fully understand how NAT works, you must understand how a PPP connection is established and IP addresses are negotiated.