ZyXEL 202H 91-003-194003B User Manual

P-202H Plus v2 User’s Guide

Chapter 25 Filter Configuration

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This chapter shows you how to create and apply filters.

Your ZyXEL Device uses filters to decide whether to allow passage of a data packet and/or to 
make a call. There are two types of filter applications: data filtering and call filtering. Filters 
are subdivided into device and protocol filters, which are discussed later.

Data filtering screens the data to determine if the packet should be allowed to pass. Data filters 
are divided into incoming and outgoing filters, depending on the direction of the packet 
relative to a port. Data filtering can be applied on either the WAN side or the LAN side. Call 
filtering is used to determine if a packet should be allowed to trigger a call. 

Outgoing packets must undergo data filtering before they encounter call filtering. Call filters 
are divided into two groups, the built-in call filters and user-defined call filters. Your ZyXEL 
Device has built-in call filters that prevent administrative, for example, RIP packets from 
triggering calls. These filters are always enabled and not accessible to you. Your ZyXEL 
Device applies the built-in filters first and then the user-defined call filters, if applicable, as 
shown next.

Figure 135   Outgoing Packet Filtering Process

For incoming packets, your ZyXEL Device applies data filters only. Packets are processed 
depending on whether a match is found. The following sections describe how to configure 
filter sets.