ZyXEL Communications ZyXEL Prestige 202, User Manual

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Prestige 202 ISDN Router
Filter Configuration
9-1
Chapter 9
Filter Configuration
This chapter shows you how to create and apply filter(s).
9.1 About Filtering
Your Prestige uses filters to decide whether or not 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 Ethernet 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 Prestige has
built-in call filters that prevent administrative, e.g., RIP packets from triggering calls. These filters
are always enabled and not accessible to you. Your Prestige applies the built-in filters first and then
the user-defined call filters, if applicable, as illustrated
in Figure 9-2 Outgoing Packet Filtering
Process .
Two sets of factory filter rules have been configured in Menu 21 to prevent NetBIOS traffic from
triggering calls. A summary of their filter rules is shown in the figures that follow.
The following diagram illustrates the logic flow when executing a filter rule.