Netgear C7100V User Manual - Page 114

Application Example: Port Triggering for Internet Relay Chat, Service Type, Starting Port, Ending Port

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AC1900 Cable Modem Voice Router 10. In the Service Type fields, enter the starting and ending ports. 11. Enter the inbound connection port information in the Starting Port and Ending Port fields. 12. Click the Apply button. The service is now in the Portmap table. You must enable port triggering before the modem router uses port triggering for the service that you added. 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 this port triggering rule you 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. Noting your port triggering rule and observing the destination port number of 6667, your 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 then removes the session information from its session table, and incoming traffic is no longer accepted on port numbers 33333 or 113. Specify Internet Port Settings 114

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Specify Internet Port Settings
114
AC1900 Cable Modem Voice Router
10.
In the
Service Type
fields, enter the starting and ending ports.
11.
Enter the inbound connection port information in the
Starting Port
and
Ending Port
fields.
12.
Click the
Apply
button.
The service is now in the Portmap table. You must enable port triggering before the
modem router uses port triggering for the service that you added.
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 this port triggering rule you 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.
Noting your port triggering rule and observing the destination port number of 6667, your
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 then removes the session information
from its session table, and incoming traffic is no longer accepted on port numbers 33333 or
113.