Chapter 10; Filter Configuration; About Filtering - ZyXEL Communications Prestige 128IMH User Manual

Prestige 128IMH ISDN Modem/ Router/Hub

Chapter 10

Filter Configuration

10.1 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 filters: data filters and call filters.
Data filters screen the data to determine if the packet should be allowed to pass. Data filters are
further divided into incoming and outgoing filters, depending on the direction of the packet
relative to a port. Call filters are used to determine if a packet should be allowed to trigger a call.
Outgoing packets must pass through the data filters before they encounter the call filters. 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 and SAP (Service
Advertising Protocol), 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 the figure below, Figure 10-1 Outgoing Packet Filtering
Process.
Filter Configuration 10-1