Filter Structure; Figure 53 Outgoing Packet Filtering Process - Nortel BCM50a Configuration Manual

118 Chapter 11 Filter configuration

Figure 53 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 BCM50a Integrated 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 BCM50a Integrated 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 54
Figure 58
N0115791
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