ZyXEL Communications PRESTIGE 128MH - Manual (Page 131)

Prestige 128MH PSTN Router/Hub
Filter Configuration 9-1
Chapter 9
Filter Configuration
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 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
direction 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 Figure 9-1, Outgoing Packet Filtering Process.