ZyXEL Communications 2864I - Manual (Page 106)

Filter Configuration 93
Filter Configuration
About Filtering
The Prestige uses filters to decide whether or not 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 10-1 Outgoing packet filtering Process