D-Link DFL-600 Manual page 46

Port Range
Direction
the protocol is identified by name.
For example, the Simple Mail Transfer Protocol
(SMTP in the drop-down menu) is used to send
and receive e-mail. It uses the TCP transport
protocol and port number 25. This information
will be entered for you, if you select SMTP from
the Protocol drop-down menu.
You can enter a range of port numbers for which
the current policy rules will be applied. If you
have only one port number to enter, enter it in
both fields.
This allows you to specify the source of network
traffic for which the current policy entry will be
applied − from the Internet (Inbound), or from
your LAN (Outbound).
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