The Port Mapping Window allows you to view and modify the Network Address Translation (NAT) table used for IP masquerading. The table at the top of the window displays the current translation entries and can be updated by pressing the "Refresh" or "Monitor" button. Uncheck "Show Permanent Only" and press Monitor to see the entire NAT table.
To Add or Remove a NAT table entry, select a row from the table if desired. This will copy the corresponding information to the edit fields in the "Configure Entry" area. Use the edit fields and controls in this area to change the information as desired, and then press "Add" or "Remove" to update the table.
You can map a range of ports by specifing a starting and ending port number separated by a hyphen for the apparent endpoint, and starting port number for the actual endpoint. For example: "6000-7000" would map all ports in the range 6000 to 7000.
NAT table entries are created dynamically when a host on your private LAN accesses the public Internet. To allow hosts on the public Internet to initiate a connection to a host on your private LAN, you can create a "permanent" translation entry. Dynamic entries are aged periodically and automatically deleted when they are no longer needed. Permanent entries remain in the table until you remove them or quit the application. Permanent entries can be saved and later restored by opening the corresponding configuration document.
The NAT table is re-initialized with any Permanent entries each time IP masquerading is enabled or when a PPP connection is established. Since it is common to masquerade behind a PPP interface with a dynamically assigned IP address, the Apparent Endpoint of each NAT table entry is automatically updated to the new PPP address unless the entry is designated as Static. Static port map entries can be used to map other fixed IP addresses to hosts on your LAN. You can use protocol port zero to map all ports for a specified address.
The "Age" column in the table indicates the number of 30 second intervals since this entry was last used. If a dynamic entry has not been used in over 60 intervals (30 minutes) it is automatically deleted. When a TCP connection is Reset or closed from both ends, the entry is set to be deleted in one minute.
The "Flags" column indicates the type and status of each entry as follows:
P Permanent entry
FL Local host has closed connection (TCP FIN packet)
FR Remote host has closed connection (TCP FIN packet)
S Static entry
Special Cases (experimental):
If you specify an actual endpoint of 0.0.0.1:0, the apparent IP address will be used as a secondary NAT address allowing datagrams received on this address to be translated for use with Telco Return cable modems.
Detailed instructions for using IPNetRouter are available on the Sustainable Softworks web site at <http://www.sustworks.com>.
