How the Modem Router Implements the Port Forwarding Rule
The following sequence shows the effects of a port forwarding rule:
1. When you enter the URL www.example.com in your browser, the browser sends a web page request
message with the following destination information:
• Destination address.The IP address of www.example.com, which is the address of your modem
router.
• Destination port number. 80, which is the standard port number for a web server process.
2. The modem router receives the message and finds your port forwarding rule for incoming port 80 traffic.
3. The modem router changes the destination IP address in the message to 192.168.0.123 and sends the
message to that computer.
4. Your web server at IP address 192.168.0.123 receives the request and sends a reply message to your
modem router.
5. Your modem router performs Network Address Translation (NAT) on the source IP address and sends
the reply through the Internet to the computer or mobile device device that sent the web page request.
Manage Port Triggering for Services and Applications
Port triggering is a dynamic extension of port forwarding that is useful in these cases:
• An application must use port forwarding to more than one local computer (but not simultaneously).
• An application must open incoming ports that are different from the outgoing port.
With port triggering, the modem router monitors traffic to the Internet from an outbound “trigger” port that
you specify. For outbound traffic from that port, the modem router saves the IP address of the computer
that sent the traffic.The modem router temporarily opens the incoming port or ports that you specify in your
rule and forwards that incoming traffic to that destination.
Port forwarding creates a static mapping of a port number or range of ports to a single local computer. Port
triggering can dynamically open ports to any computer when needed and close the ports when they are no
longer needed.
If you use applications such as multiplayer gaming, peer-to-peer connections, real-time
communications such as instant messaging, or remote assistance, enable Universal
Plug-N-Play (UPnP). See Improve Network Connections With Universal Plug-N-Play on
page 112.
Note
Add a Port Triggering Rule
The modem router does not provide default services and applications for port triggering rules.You must
define a custom service or application for each port triggering rule.
Manage Port Forwarding and Port Triggering
193
Nighthawk AC1900 WiFi VDSL/ADSL Modem Router Model D7000v2
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