ZyXEL Communications Internet Security Gateway ZyWALL 2 Series - Manual (Page 437)

ZyWALL 2 Series User’s Guide
Filter Configuration 30-1
Chapter 30
Filter Configuration
This chapter shows you how to create and apply filters.
30.1 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.