Nortel Networks WEB OS 212777 - Manual (Page 169)

212777-A, February 2002
169
C
HAPTER
7
Filtering
This chapter provides a conceptual overview of filters and includes configuration examples
showing how filters can be used for network security and Network Address Translation (NAT).
The following topics are discussed in this chapter:
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“Overview” on page 170 . This section describes the benefits and filtering criteria to allow
for extensive filtering at the IP and TCP/UDP levels.
o “Filtering Benefits” on page 170
o “Filtering Criteria” on page 170
o “Stacking Filters” on page 172
o “Overlapping Filters” on page 172
o “The Default Filter” on page 173
o “VLAN-based Filtering” on page 174
o “Optimizing Filter Performance” on page 176
o “Filter Logs” on page 176
o “IP Address Ranges” on page 178
o “Cache-Enabled versus Cache-Disabled Filters” on page 178
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“TCP Rate Limiting” on page 179 . This section explains how TCP rate limiting allows
you to monitor the number of new TCP connections within a configurable time window.
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“Tunable Hash for Filter Redirection” on page 184 allows you to select any hash parame-
ter for filter redirection.
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“Filter-based Security” on page 185 . This section provides an example of configuring fil-
ters for providing the best security.
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“Network Address Translation” on page 191 . This section provides two examples: Internal
client access to the Internet and external client access to the server.
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“Matching TCP Flags” on page 197 and “Matching ICMP Message Types” on page 201 .
Describes the ACK filter criteria which provides greater filtering flexibility and lists
ICMP message types that can be filtered respectively.