The BASIC Home page displays.
5. Select ADVANCED > Advanced Setup > Port Forwarding / Port Triggering.
The Port Forwarding / Port Triggering page displays.
6. Select the Port Triggering radio button.
The port triggering settings display.
7. Select the Disable Port Triggering check box.
If this check box is selected, the modem router does not apply port triggering rules even if you specified
them.
8. Click the Apply button.
Your settings are saved.
Application Example: Port Triggering for Internet Relay Chat
Some application servers, such as FTP and IRC servers, send replies to multiple port numbers. Using
port triggering, you can tell the modem router to open more incoming ports when a particular outgoing
port starts a session.
An example is Internet Relay Chat (IRC).Your computer connects to an IRC server at destination port
6667.The IRC server not only responds to your originating source port but also sends an “identify” message
to your computer on port 113. Using port triggering, you can tell the modem router, “When you initiate a
session with destination port 6667, you must also allow incoming traffic on port 113 to reach the originating
computer.”
The following sequence shows the effects of this port triggering rule:
1. You open an IRC client program to start a chat session on your computer.
2. Your IRC client composes a request message to an IRC server using a destination port number of
6667, the standard port number for an IRC server process.Your computer then sends this request
message to your modem router.
3. Your modem router creates an entry in its internal session table describing this communication session
between your computer and the IRC server.Your modem router stores the original information,
performs Network Address Translation (NAT) on the source address and port, and sends this request
message through the Internet to the IRC server.
4. Noting your port triggering rule and observing the destination port number of 6667, your modem router
creates another session entry to send any incoming port 113 traffic to your computer.
5. The IRC server sends a return message to your modem router using the NAT-assigned source port
(for example, port 33333) as the destination port and also sends an “identify” message to your modem
router with destination port 113.
6. When your modem router receives the incoming message to destination port 33333, it checks its
session table to see if a session is active for port number 33333. Finding an active session, the modem
Manage Port Forwarding and Port Triggering
290
Nighthawk AC1900 WiFi VDSL/ADSL Modem Router Model D7000
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