Configuring Filters; Figure 9-1. Outgoing Packet Filtering Process - NETGEAR RT338 Reference Manual

This chapter describes how to use and configure filters for your Model RT338 ISDN Router.
The router uses filters to decide whether to allow passage of a data packet and/or to make a call
over the ISDN line. Three types of filters are involved: incoming data filters, outgoing data filters,
and 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 call filters.
The call filters are divided into two groups: default call filters and user-defined call filters.
The Model RT338 router has default call filters that filter out administrative packets (for example,
RIP packets). The router applies the default filters first and then, if applicable, applies the
user-defined call filters as shown in
Outgoing Data
packet filters
Drop
packet
Figure 9-1. Outgoing Packet Filtering Process
For incoming packets, the router applies data filters only. Packets are processed depending on
whether or not a match is made. The router lets you customize the filter sets that you want to use.
The following sections describe how to configure the filter sets for the router.

Configuring Filters

Figure
No
match
Built-in
default call
filters
Match
Drop packet
if line not up
Configuring Filters
9-1.
Call filters
No
match
User-defined
call filters
(if applicable)
Match Match
Drop packet
if line not up
Or
Send packet
but do not
reset idle timer
Chapter 9
No Active data
match
Initiate call
if line not up
Send packet
and reset
idle timer
Or
Send packet
but do not
reset idle timer
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9-1