NETGEAR D6400 User Manual page 275

AC1600 WiFi VDSL/ADSL Modem Router Model D6400
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.
Manage Port Forwarding and Port Triggering
275