RadioLAN WNR834B - Manual (Page 68)

NETGEAR RangeMax™ NEXT Wireless Router WNR834B User Manual
6-4 Fine-Tuning Your Network
v1.2, January 2007
a. You open an IRC client program, beginning a chat session on your computer.
b. 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 router.
c. Your router creates an entry in its internal session table describing this communication
session between your computer and the IRC server. Your 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.
d. Noting your Port Triggering rule, and having observed the destination port number
of 6667, your router creates an additional session entry to send any incoming port
113 traffic to your computer.
e. The IRC server sends a return message to your router using the NAT-assigned source port
(as in the previous example, let’s say port 33333) as the destination port. The IRC server
also sends an “identify” message to your router with destination port 113.
f. Upon receiving the incoming message to destination port 33333, your router checks its
session table to determine whether there is an active session for port number 33333.
Finding an active session, the router restores the original address information replaced by
NAT and sends this reply message to your computer.
g. Upon receiving the incoming message to destination port 113, your router checks its
session table and learns that there is an active session for port 113, associated with
your computer. The router replaces the message’s destination IP address with your
computer’s IP address and forwards the message to your computer.
h. When you finish your chat session, your router eventually senses a period of inactivity in
the communications. The router then removes the session information from its session
table, and incoming traffic is no longer accepted on port numbers 33333 or 113.
To configure Port Triggering, you need to know which inbound ports the application needs. Also,
you need to know the outbound port number that will trigger the opening of the inbound ports.
This information can usually be determined by contacting the publisher of the application or from
user groups or newsgroups..
Note: Only one computer at a time can use the triggered application.