ZyXEL Communications ZyWALL 2 Plus - Manual (Page 541)

ZyWALL 2 Plus User’s Guide
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H A P T E R
38
Filter Configuration
This chapter shows you how to create and apply filters.
38.1 Introduction to Filters
Your ZyWALL 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. Remote node call
filtering is only applicable when using PPPoE encapsulation. Outgoing packets must undergo
data filtering before they encounter call filtering as shown in the following figure.
Figure 367 Outgoing Packet Filtering Process
For incoming packets, your ZyWALL applies data filters only. Packets are processed
depending upon whether a match is found. The following sections describe how to configure
filter sets.