User`s guide

Pipeline User’s Guide Preliminary January 30, 1998 6-1
6
Defining Filters and Firewalls
This chapter contains the following topics:
Introduction to filters
Filters inspect packets, and depending on the attributes of the packet, filters reject
packets from entering or leaving your network. When a filter is in use, the
Pipeline examines every packet in the packet stream and takes action if the
defined filter conditions are present. The action the Pipeline takes depends both
on the conditions specified within the filter and how the filter is applied.
The default action when no filter is used is to forward (accept) all packets and
allow all packets to reset the idle timer, which is used to determine when to
disconnect inactive sessions.
Introduction to filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Overview of Filter profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
Example filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12
Working with predefined call filters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
Display unwanted dial-out packets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-28
Secure Access Firewalls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-34
Filter persistence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-36