Filter Structure; Figure 61 Outgoing Packet Filtering Process - Nortel 222 User Manual

136 Chapter 11 Filter configuration

Figure 61 Outgoing packet filtering process

D a t a
O u t g o in g
F ilt e r in g
P a c k e t
M a t c h
D r o p
p a c k e t
For incoming packets, your Business Secure Router applies data filters only.
Packets are processed depending upon whether a match is found. The following
sections describe how to configure filter sets.

Filter Structure

A filter set consists of one or more filter rules. Usually, you group related rules,
for example, all the rules for NetBIOS, into a single set and give it a descriptive
name. With the Business Secure Router, you can configure up to twelve filter sets
with six rules in each set, for a total of 72 filter rules in the system. You cannot
mix device filter rules and protocol filter rules within the same set. You can apply
up to four filter sets to a particular port to block multiple types of packets. With
each filter set having up to six rules, you can have a maximum of 24 rules active
for a single port.
Sets of factory default filter rules are configured in menu 21 to prevent NetBIOS
traffic from triggering calls and to prevent incoming Telnet sessions. A summary
of their filter rules is shown in the figures that follow.
Figure 62
Figure 66
NN47922-501
N o
B u ilt - in
m a t c h
d e f a u lt
C a ll F ilt e r s
M a t c h
D r o p p a c k e t
if lin e n o t u p
O r
illustrates the logic flow when executing a filter rule. Also see
for the logic flow when executing an IP filter.
C a ll F ilt e r in g
N o
U s e r - d e f in e d
m a t c h
C a ll F ilt e r s
( if a p p lic a b le )
M a t c h
D r o p p a c k e t
if lin e n o t u p
O r
S e n d p a c k e t
b u t d o n o t r e s e t b u t d o n o t r e s e t
I d le T im e r
A c t iv e D a t a
N o
m a t c h
I n it ia t e c a ll
if lin e n o t u p
S e n d p a c k e t
a n d r e s e t
I d le T im e r
S e n d p a c k e t
I d le T im e r