tunnel. This arrangement is illustrated in the diagram below.
Figure 7.4. Anonymizing with NAT
NetDefendOS is set up with
NAT
rules in the IP rule set so it takes communication traffic coming
from the client and NATs it back out onto the Internet. Communication with the client is with the
PPTP protocol but the PPTP tunnel from the client terminates at the firewall. When this traffic is
relayed between the firewall and the Internet, it is no longer encapsulated by PPTP.
When an application, such as a web server, now receives requests from the client it appears as
though they are coming from the anonymizing service provider's external IP address and not the
client's IP. The application therefore sends its responses back to the firewall which relays the
traffic back to the client through the PPTP tunnel. The original IP address of the client is not
revealed in traffic as it is relayed beyond the termination of the PPTP tunnel at the NetDefendOS.
Typically, all traffic passes through the same physical interface and that interface has a single
public IP address. Multiple interfaces could be used if multiple public IPv4 addresses are
available. There is clearly a small processing overhead involved with anonymizing traffic but this
need not be an issue if sufficient hardware resources are employed to perform the anonymizing.
This same technique can also be used with L2TP instead of PPTP connections. Both protocols are
discussed further in
Section 9.5.4, “PPTP/L2TP Clients”
.
Chapter 7: Address Translation
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Summary of Contents for NetDefendOS
Page 30: ...Figure 1 3 Packet Flow Schematic Part III Chapter 1 NetDefendOS Overview 30 ...
Page 32: ...Chapter 1 NetDefendOS Overview 32 ...
Page 144: ...Chapter 2 Management and Maintenance 144 ...
Page 284: ...Chapter 3 Fundamentals 284 ...
Page 392: ...Chapter 4 Routing 392 ...
Page 419: ... Host 2001 DB8 1 MAC 00 90 12 13 14 15 5 Click OK Chapter 5 DHCP Services 419 ...
Page 420: ...Chapter 5 DHCP Services 420 ...
Page 573: ...Chapter 6 Security Mechanisms 573 ...
Page 607: ...Chapter 7 Address Translation 607 ...
Page 666: ...Chapter 8 User Authentication 666 ...
Page 775: ...Chapter 9 VPN 775 ...
Page 819: ...Chapter 10 Traffic Management 819 ...
Page 842: ...Chapter 11 High Availability 842 ...
Page 866: ...Default Enabled Chapter 13 Advanced Settings 866 ...
Page 879: ...Chapter 13 Advanced Settings 879 ...