SMC Networks SMC7004VBR V.2 - Manual (Page 37)

Advanced Setup
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[Special Applications]
Some applications, such as Internet gaming, videoconferencing,
Internet telephony require multiple connections. These
applications cannot work with Network Address Translation
(NAT) enabled. If you need to run applications that require
multiple connections, use the following screen to specify
the additional public ports to be opened for each application.
Specify the port or port range normally associated with an
application in the [Trigger Port/s] field, select the protocol type
as TCP or UDP, and then enter the public ports and data type
associated with the trigger port to open them for inbound traffic.
The maximum range that you can use for all NAT ports
is 0 to 65535.