Port Triggering; Figure 12-12: Port Triggering - AudioCodes MP-202 User Manual

MP-202 Telephone Adapter
12.5

Port Triggering

Port triggering can be used for dynamic port forwarding configuration. By setting port
triggering rules, you can allow inbound traffic to arrive at a specific LAN host, using ports
different than those used for the outbound traffic. This is called port triggering since the
outbound traffic triggers to which ports inbound traffic is directed.
For example, consider a gaming server that is accessed using UDP protocol on port 2222.
The gaming server responds by connecting the user using UDP on port 3333 when starting
gaming sessions. In such a case you must use port triggering, since this scenario conflicts
with the following default firewall settings:
The firewall blocks inbound traffic by default.
The server replies to the gateway's IP, and the connection is not sent back to your
host, since it is not part of a session.
To solve this, you need to define a Port Triggering entry, which allows inbound traffic on
UDP port 3333, only after a LAN host generated traffic to UDP port 2222. This results in
accepting the inbound traffic from the gaming server and sending it back to the LAN Host
which originated the outgoing traffic to UDP port 2222.
Select the tab 'Port Triggering' in the 'Security' screen; the screen 'Port Triggering' opens
(refer to the figure). The screen lists all port triggering entries.
Version 2.6

Figure 12-12: Port Triggering

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12. Security
May 1