ZyXEL Communications Prestige 128IMH, User Manual

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Prestige 128IMH User’s Guide ZyXEL
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Page 12-1
12. Filter Configuration
12.1. About Filtering
The Prestige uses filters to decide whether to allow passage of a data packet and/or to make
a call over the ISDN line. There are three types of filters involved: incoming data filters,
outgoing data filters and call filters. Data filters screen the data to determine if the packet
should be allowed to pass. Call filters are used to determine if a call should be placed.
Outgoing packets must pass through the data filters before they encounter the call filters.
Call filters are divided into two groups: default call filters and user-defined call filters.
Prestige has default call filters that filter out administrative packets, e.g., RIP and SAP
packets. The Prestige applies the default filters first and then the user-defined call filters if
applicable as seen below:
Figure 12-1 Outgoing Packet Filtering Process
For incoming packets, the Prestige applies data filters only. Packets are processed
depending upon whether a match is made. The Prestige allows you to customize the filter
sets that you wish to use. These following sections describe how to configure the Prestige’s
filter sets.