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Never. The modem router does not use port triggering even if you have specified port
triggering settings.
•
Per Schedule. Port triggering is used based on the settings in the Schedule screen.
•
Always. Always use port triggering.
7.
In the Port Triggering Timeout field, enter a value up to 9999 minutes.
This value controls how long the inbound ports stay open when the modem router detects
no activity. This value is required because the modem 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 modem 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 modem 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.
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 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
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.
Based on the port triggering rule with the destination port number of 6667, the modem router
creates another session entry to send any incoming port 113 traffic to your computer.
5.
The IRC server sends a return message to your modem router using the NAT-assigned
source port (for example, port 33333) as the destination port. The IRC server also sends an
"identify" message to your modem router with destination port 113.
6.
When your modem router receives the incoming message to destination port 33333, it
checks its session table to see if a session is active for port number 33333. Finding an active
session, the modem router restores the original address information replaced by NAT and
sends this reply message to your computer.
7.
When your modem router receives the incoming message to destination port 113, it checks
its session table and finds an active session for port 113 associated with your computer. The
modem router replaces the message's destination IP address with your computer's IP
address and forwards the message to your computer.
8.
When you finish your chat session, your modem router eventually senses a period of
inactivity in the communications. The modem router removes the session information from
its session table, and incoming traffic is no longer accepted on port numbers 33333 or 113.
N300 WiFi Cable Modem Router Model C3000
Specify Internet Port Settings
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