How Port Forwarding Differs From Port Triggering - NETGEAR RANGEMAX WNR3500L User Manual

RangeMax™ Wireless-N Gigabit Router with USB WNR3500L User Manual
1. The user of a remote computer opens Internet Explorer and requests a Web page from
www.example.com, which resolves to the public IP address of your router. The remote
computer composes a Web page request message with the following destination information:
• The destination address is the IP address of www.example.com, which is the address of
your router.
• The destination port number is 80, the standard port number for a Web server process.
The remote computer then sends this request message through the Internet to your router.
2. Your router receives the request message and looks in its rules table for any rules covering the
disposition of incoming port 80 traffic. Your port forwarding rule specifies that incoming port
80 traffic should be forwarded to local IP address 192.168.1.123. Therefore, your router
modifies the destination information in the request message:
The destination address is replaced with 192.168.1.123.
Your router then sends this request message to your local network.
3. Your Web server at 192.168.1.123 receives the request and composes a return message with
the requested Web page data. Your Web server then sends this reply message to your router.
4. Your router performs Network Address Translation (NAT) on the source IP address, and sends
this request message through the Internet to the remote computer, which displays the Web
page from www.example.com.
To configure port forwarding, you need to know which inbound ports the application needs. You
usually can determine this information by contacting the publisher of the application or user
groups or newsgroups.

How Port Forwarding Differs from Port Triggering

The following points summarize the differences between port forwarding and port triggering:
• Port triggering can be used by any computer on your network, although only one computer at a
time can use the same ports.
• Port forwarding is configured for a single computer on your network.
• Port triggering does not need to know the computer's IP address in advance. The IP address is
captured automatically.
• Port forwarding requires that you specify the computer's IP address during configuration, and
the IP address must never change.
• Port triggering requires specific outbound traffic to open the inbound ports, and the triggered
ports are closed after a period of no activity.
• Port forwarding is always active and does not need to be triggered.
Customizing Your Network Settings
v1.0, November 2009
5-15