Nortel BCM50a, Руководство по настройке

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118 Chapter 11 Filter configuration
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Figure 53 Outgoing packet filtering process
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 illustrates the logic flow when executing a filter rule. Also see
Figure 58 for the logic flow when executing an IP filter.
Data
Filtering
O utgoing
Packet
D rop
packet
Built-in
default
C all Filters
U ser-defined
Call Filters
(if applicable)
Initiate call
if line not up
Active Data
Send packet
and reset
Idle Tim er
O r O r
Drop packet
if line not up D rop packet
if line not up
Send packet
but do not reset
Idle Tim er
Send packet
but do not reset
Idle Tim er
M atch M atch M atch
No
m atch
N o
m atch
N o
m atch
C all Filtering