Netgear DGN1000v3 User Manual download pdf (Page 102)

Advanced Settings

102

N150 Wireless ADSL2+ Modem Router DGN1000v3

Your modem router then sends this request message through the Internet to the web

server at www.example.com.

4. The web server at www.example.com composes a return message with the requested web

page data. The return message contains the following address and port information. The

web server then sends this reply message to your modem router:

• Source address.

The IP address of www

.example.com

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

• Destination address.

The public IP address of your modem router

• Destination port number. 33333

5. Upon receiving the incoming message, your modem router checks its session table to

determine whether there is an active session for port number 33333. Finding an active

session, the

modem router then modifies the message to restore the original address

information replaced by NA

. Your modem router sends this reply message to your

computer, which displays the web page from www.example.com. The message now

contains the following address and port information:

• Source address.

The IP address of www

.example.com

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

• Destination address.

our computer’s IP address

• Destination port number. 5678, which is the browser session that made the initial

request

6. When you finish your browser session, your modem router eventually detects a period of

inactivity in the communications.

our modem router then removes the session information

from its session table, and incoming traffic is no longer accepted on port number 33333.

Port Triggering to Open Incoming Ports

Some application servers (such as FTP and IRC servers) send replies to multiple port

numbers. Using the port triggering function of your modem router, you can tell the modem

router to open more incoming ports when a particular outgoing port originates 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 1

13. Using port triggering, you can

tell the modem router, “When you initiate a session with destination port 6667, you need to

also allow incoming traffic on port 113 to reach the originating computer.” Using steps similar

to the preceding example, 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. 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

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