Port Triggering To Open Incoming Ports - NETGEAR D6300 User Manual

Destination port number. 5678, which is the browser session that made the initial
request.
When you finish your browser session, your WiFi modem router eventually detects a period
6.
of inactivity in the communications. Your WiFi 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

In the preceding example, requests are sent to a remote computer by your WiFi modem
router from a particular service port number, and replies from the remote computer to your
WiFi modem router are directed to that port number. If the remote server sends a reply to a
different port number, your WiFi modem router does not recognize it and discards it.
However, some application servers (such as FTP and IRC servers) send replies to multiple
port numbers. Using the port triggering function of your WiFi modem router, you can tell the
WiFi modem router to open additional 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 113. Using port triggering, you can
tell the WiFi modem router, "When you initiate a session with destination port 6667, you have
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. You 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 WiFi modem router.
3. Your WiFi modem router creates an entry in its internal session table describing this
communication session between your computer and the IRC server. Your WiFi modem
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 having observed the destination port number of 6667,
your WiFi modem router creates an additional session entry to send any incoming port 113
traffic to your computer.
5. The IRC server sends a return message to your WiFi modem router using the
NAT-assigned source port (as in the previous example, say port 33333) as the destination
port. The IRC server also sends an identify message to your WiFi modem router with
destination port 113.
6. Upon receiving the incoming message to destination port 33333, your WiFi modem router
checks its session table to determine whether there is an active session for port number
33333. Finding an active session, the WiFi modem router restores the original address
information replaced by NAT and sends this reply message to your computer.
D6300 WiFi DSL Modem Router
Advanced Settings
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