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Prestige 645R-A Series User’s Guide
16-14 NAT
16.5.3 Example 3: Multiple Public IP Addresses With Inside Servers
In this example, there are 3 IGAs from our ISP. There are many departments but two have their own FTP
server. All departments share the same router. The example will reserve one IGA for each department with
an FTP server and all departments use the other IGA. Map the FTP servers to the first two IGAs and the
other LAN traffic to the remaining IGA. Map the third IGA to an inside web server and mail server. Four
rules need to be configured, two bi-directional and two uni-directional as follows.
Rule 1. Map the first IGA to the first inside FTP server for FTP traffic in both directions (1 : 1
mapping, giving both local and global IP addresses).
Rule 2. Map the second IGA to our second inside FTP server for FTP traffic in both directions (1 : 1
mapping, giving both local and global IP addresses).
Rule 3. Map the other outgoing LAN traffic to IGA3 (Many : 1 mapping).
Rule 4. You also map your third IGA to the web server and mail server on the LAN. Type Server
allows you to specify multiple servers, of different types, to other computers behind NAT on the
LAN.
The example situation looks somewhat like this:
Figure 16-15 NAT Example 3