User`s guide

Prestige 128+ ISDN Router
Filter Configuration 11-1
Chapter 11
Filter Configuration
11.1 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 11-1 Outgoing Packet
Filtering Process.