NETGEAR CBK40 User Manual page 79

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 cable modem router.
3. Your cable modem router creates an entry in its internal session table describing this communication
session between your computer and the IRC server. Your cable 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 cable 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 cable 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 cable modem router with destination port 113.
6. When your cable 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 cable
modem router restores the original address information replaced by NAT and sends this reply message
to your computer.
7. When your cable 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 cable 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 cable modem router eventually senses a period of inactivity in
the communications. The cable modem router then removes the session information from its session
table, and incoming traffic is no longer accepted on port numbers 33333 or 113.
Orbi WiFi System
Customize Internet Traffic Rules for Ports
79