Netopia 4753 manual Input and output filters-source and destination, Netopia R-Series Router

Security 13-13

Input and output filters—source and destination

There are two kinds of filters you can add to a filter set: input and output. Input filters check packets received from the Internet, destined for your network. Output filters check packets transmitted from your network to the Internet.

	packet
WAN	input filter
	LAN
	packet
	output filter
	The Netopia R-Series Router

Packets in the Netopia 4753 pass through an input filter if they originate in the WAN and through an output filter if they’re being sent out to the WAN.

The process for adding input and output filters is exactly the same. The main difference between the two involves their reference to source and destination. From the perspective of an input filter, your local network is the destination of the packets it checks, and the remote network is their source. From the perspective of an output filter, your local network is the source of the packets, and the remote network is their destination.

Type of filter	Source means	Destination means
Input filter	The remote network	The local network
Output filter	The local network	The remote network

Adding filters to a filter set

In this section you’ll learn how to add an input filter to a filter set. Adding an output filter works exactly the same way, providing you keep the different source and destination perspectives in mind.

To add an input filter, select Add Input Filter in the Add IP Filter Set screen. The Add Filter screen appears. (To add an output filter, select Add Output Filter.)