Port Forwarding To Permit External Host Communications - NETGEAR CG3300CMR User Manual

also sends an "identify" message to your computer on port 113. Using port triggering, you can
tell the gateway, "When you initiate a session with destination port 6667, you have to allow
incoming traffic also 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:
You open an IRC client program to start a chat session on your computer.
1.
Your IRC client composes a request message to an IRC server using a destination port
2.
number of 6667, the standard port number for an IRC server process. Your computer then
sends this request message to your gateway.
Your gateway creates an entry in its internal session table describing this communication
3.
session between your computer and the IRC server. Your gateway 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.
Noting your port triggering rule and having observed the destination port number of 6667,
4.
your gateway creates an additional session entry to send any incoming port 113 traffic to
your computer.
The IRC server sends a return message to your gateway using the NAT-assigned source
5.
port (as in the previous example, say port 33333) as the destination port. The IRC server
also sends an identify message to your gateway with destination port 113.
Upon receiving the incoming message to destination port 33333, your gateway checks its
6.
session table to determine whether there is an active session for port number 33333.
Finding an active session, the gateway restores the original address information that is
replaced by NAT and sends this reply message to your computer.
Upon receiving the incoming message to destination port 113, your gateway checks its
7.
session table and learns that there is an active session for port 113, associated with your
computer. The gateway replaces the destination IP address of the message with the IP
address of your computer and forwards the message to your computer.
When you finish your chat session, your gateway eventually senses a period of inactivity in
8.
the communications. The gateway then removes the session information from its session
table, and incoming traffic is no longer accepted on ports 33333 or 113.
To configure port triggering, you need to know which inbound ports the application needs.
Also, you need to know the number of the outbound port that triggers the opening of the
inbound ports. You can usually determine this information by contacting the publisher of the
application or user groups or newsgroups.
Only one computer at a time can use the triggered application.
Note:

Port Forwarding to Permit External Host Communications

In both of the preceding examples, your computer initiates an application session with a
server computer on the Internet. However, you need to allow a client computer on the
Internet to initiate a connection to a server computer on your network. Normally, your
gateway ignores any inbound traffic that is not a response to your own outbound traffic. You
can configure exceptions to this default rule by using the port forwarding feature.
Wireless Cable Gateway CG3300CMR
Advanced Settings
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