ZyXEL Communications 128MH - Manual (Page 127)

Prestige 128MH PSTN Router/Hub
9-1 Chapter 9 Filter Configuration
Chapter 9
Filter Configuration
About Filtering
Your Prestige uses filters to decide whether or not to allow passage of a data packet and/or to
make a call over the Modem or ISDN TA line. There are three types of filters involved:
l Incoming Data Filters
l Outgoing Data Filters
l 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
l Default Call Filters
l User-defined Call Filters.
Your Prestige has default call filters that filter out administrative packets (for example, RIP and
SAP packets). Your Prestige applies the default filters first and then the user-defined call filters if
applicable as the outgoing packet filtering process illustrates in Figure 9-1.