Netgear AC1600 Owner's Manual

When you finish your chat session, your router eventually senses a period of inactivity in the 

communications. The router then removes the session information from its session table, 

and incoming traffic is no longer accepted on port numbers 33333 or 113.

To configure port triggering, you need to know which inbound ports the application needs. 

Also, you need to know the number of the outbound port that triggers the opening of the 

inbound ports. You can usually determine this information by contacting the publisher of the 
application or the relevant user groups or news groups.

Only one computer at a time can use the triggered application.

In both of the preceding examples, your computer initiates an application session with a 
server computer on the Internet. However, you might need to allow a client computer on the 
Internet to initiate a connection to a server computer on your network. Normally, your router 
ignores any inbound traffic that is not a response to your own outbound traffic. You can 
configure exceptions to this default rule by using the port forwarding feature. 

A typical application of port forwarding can be shown by reversing the client-server 

relationship from the previous web server example. In this case, a remote computer’s 
browser needs to access a web server running on a computer in your local network. Using 
port forwarding, you can tell the router, “When you receive incoming traffic on port 80 (the 
standard port number for a web server process), forward it to the local computer at 
192.168.1.123.” The following sequence shows the effects of the port forwarding rule you 
have defined:

The user of a remote computer opens a browser 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: 

Destination address. The IP address of www.example.com, which is the address of your 
router.

Destination port number. 80, which is the standard port number for a web server 
process.

The remote computer then sends this request message through the Internet to your 
router.

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.

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.