Chapter 19 Filter Configuration; Introduction To Filters - ZyXEL Communications ZyXEL ZyWALL 2WE User Manual

ZyWALL 2 and ZyWALL 2WE
Chapter 19
Filter Configuration
This chapter shows you how to create and apply filters.

19.1 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.
Filter Configuration 19-1