Netgear LG2200D User's Guide download pdf (Page 39)

Control Access to the Internet

U.S. Cellular® 4G LTE™ Router (LG2200D)

5. Select the Port Triggering radio button.

6. Clear the Disable Port Triggering check box.

If this check box is selected, the router does not use port triggering even if you have

specified port triggering settings.

7. In the Port T

riggering Time-out field, enter a value up to 9999 minutes.

This value controls how long the inbound ports stay open when the router detects no

activity

. This value is required because the router cannot detect when the application

terminates.

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 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 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 the port triggering rule you have defined:

1. Y

ou open an IRC client program to start a chat session on your computer.

2. Y

our 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 router.

3. Y

our router creates an entry in its internal session table describing this communication

session between your computer and the IRC server. Your 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

router creates another session entry to send any incoming port 1

13 traffic to your computer.

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Netgear LG2200D User's Guide Page 39