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NAT
Table 11-7 Services & Port Numbers
SERVICES
PORT NUMBER
ECHO
7
FTP (File Transfer Protocol)
21
Telnet
23
SMTP (Simple Mail Transfer Protocol)
25
DNS (Domain Name System)
53
Finger
79
HTTP (Hyper Text Transfer protocol or WWW, Web)
80
POP3 (Post Office Protocol)
110
NNTP (Network News Transport Protocol)
119
SNMP (Simple Network Management Protocol)
161
SNMP trap
162
PPTP (Point-to-Point Tunneling Protocol)
1723
Configuring a Server behind NAT
Follow these steps to configure a server behind NAT:
Step 1.
Enter 15 in the main menu to go to
Menu 15 - NAT Setup.
Step 2.
Enter 2 to go to
Menu 15.2 - NAT Server Setup
.
Step 3.
Enter a port number in an unused
Start Port No
field. To forward only one port, enter it again
in the
End Port No
field. To specify a range of ports, enter the last port to be forwarded in the
End Port No
field.
Step 4.
Enter the inside IP address of the server in the
IP Address
field. In the following figure, you
have a computer acting as an FTP, Telnet and SMTP server (ports 21, 23 and 25) at
192.168.1.33.
Step 5.
Press
[ENTER]
at the “Press ENTER to confirm …” prompt to save your configuration after
you define all the servers or press
[ESC]
at any time to cancel.
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11-17
Figure 11-10 Menu 15.2 — NAT Server Setup
Figure 11-11 Multiple Servers Behind NAT Example
Menu 15.2 - NAT Server Setup
Rule
Start Port No.
End Port No.
IP Address
---------------------------------------------------
1.
Default
Default
0.0.0.0
2.
0
0
0.0.0.0
3.
0
0
0.0.0.0
4.
0
0
0.0.0.0
5.
0
0
0.0.0.0
6.
0
0
0.0.0.0
7.
0
0
0.0.0.0
8.
0
0
0.0.0.0
9.
0
0
0.0.0.0
10.
0
0
0.0.0.0
11.
0
0
0.0.0.0
12.
0
0
0.0.0.0
Press ENTER to Confirm or ESC to Cancel:
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NAT
11.3.3 Trigger Port Setup
The Prestige records the IP address of a LAN computer that requests a service that you have defined as a
“trigger port”. The response from the Internet can then be forwarded directly to the LAN computer. Trigger
ports are transient; they only exist while in use or are timed out. The following is a trigger port example
Figure 11-12 Trigger Port Forwarding Process: Example
1.
Jane requests a file from the Real Audio server (port 7070).
2.
Port 7070 is a “trigger” port and causes the Prestige to record Jane’s computer IP address. The
Prestige associates Jane's computer IP address with the "incoming" port range of 6970-7170.
3.
The Real Audio server responds using a port number ranging between 6970-7170.
4.
The Prestige forwards the traffic to Jane’s computer IP address.
5.
Only Jane can connect to the Real Audio server until the connection is closed or times out. The
Prestige times out in three minutes with UDP (User Datagram Protocol) or two hours with TCP/IP
(Transfer Control Protocol/Internet Protocol).
Two Points To Remember About Trigger Ports
1.
Trigger events only happen on outgoing data (from the Prestige to the WAN).
2.
Only one LAN computer can use a trigger port (range) at a time.
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11-19
Enter 3 in menu 15 to display
Menu 15.3 — Trigger Port Setup
, shown next.
Figure 11-13 Menu 15.3: Trigger Port Setup
Menu 15.3 - Trigger Port Setup
Incoming
Trigger
Rule
Name
Start Port
End Port
Start Port
End Port
----------------------------------------------------------------------
1.
Real Audio
6970
7170
7070
7070
2.
0
0
0
0
3.
0
0
0
0
4.
0
0
0
0
5.
0
0
0
0
6.
0
0
0
0
7.
0
0
0
0
8.
0
0
0
0
9.
0
0
0
0
10.
0
0
0
0
11.
0
0
0
0
12.
0
0
0
0
Press ENTER to Confirm or ESC to Cancel:
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NAT
Table 11-8 Menu 15.3—Trigger Port Setup Description
FIELD
EXAMPLE
Rule
This is the rule index number.
1
Name
Enter a unique name for identification purposes. You may enter up to 15
characters in this field. All characters are permitted - including spaces.
Real Audio
Incoming
Incoming is a port (or a range of ports) that a server on the WAN uses when it sends out a
particular service. The Prestige forwards the traffic with this port (or range of ports) to the
client computer on the LAN that requested the service.
Start Port
Enter a port number or the starting port number in a range of port numbers.
6970
End Port
Enter a port number or the ending port number in a range of port numbers.
7170
Trigger
The trigger port is a port (or a range of ports) that causes (or triggers) the Prestige to record
the IP address of the LAN computer that sent the traffic to a server on the WAN.
Start Port
Enter a port number or the starting port number in a range of port numbers.
7070
End Port
Enter a port number or the ending port number in a range of port numbers.
7070
Press [ENTER] at the message “Press ENTER to Confirm...” to save your configuration, or press [ESC]
at any time to cancel.
11.4 General NAT Examples
11.4.1 Internet Access Only
In the following Internet access example, you only need one rule where all your ILAs (Inside Local
addresses) map to one dynamic IGA (Inside Global Address) assigned by your ISP.
19216811.live