ZyXEL Communications 480 - Manual (Page 95)

Prestige 480 ISDN Router
Filter Configuration 7-1
Chapter 7
Filter Configuration
This chapter shows you how to create and apply filter(s).
7.1 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. These filters are further subdivided
into device and protocol filters, which are discussed later.
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 the user-defined call filters. Your
Prestige has built-in call filters that prevent administrative, e.g., RIP 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 next figure.
Figure 7-1 Outgoing Packet Filtering Process
Outgoing
Packet
Data
Filters
Drop
packet
Built-in
default
Call Filters
User-defined
Call Filters
(if applicable)
Initiate call
if line not up
Active Data
Send packet
and reset
Idle Timer
Or Or
Drop packet
if line not up Drop packet
if line not up
Send packet
but do not reset
Idle Timer
Send packet
but do not reset
Idle Timer
Match Match Match
No
match
No
match
No
match
Call Filters