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The remainder of the file is partitioned into protocol sections. Each protocol
section has a descriptive header and contains the filter rules for that protocol.
Protocol Sections
A single filter file can contain all valid protocol sections in any order, but the
sections cannot be repeated. The following conditions will generate errors or
prevent normal filtering:
If you do not specify a protocol section in the filter file, no filtering will occur
and packets of that protocol type will be accepted
If you specify a protocol section but do not define any rules, an error will occur
If you omit a line number, or insert a line out of sequence an error will occur
To comment out a protocol section, you must place a pound (#) sign before the
section header and before all rules defined in the section.
The following table describes the valid protocol sections that you can define in the
filter file:
Table 27-1
Protocol Section
IP
IP-RIP
LOGIN-ACCESS
Protocol Rules
You can define protocol rules within each protocol section in the filter file. Protocol
rules determine which packets may and may not access the network.
The rule syntax is:
<line #> <verb> <keyword> <operator> <value>;
The combination of keyword, operator, and value forms the condition which,
when combined with the verb, determines whether the packet is accepted or
rejected.
When a packet is filtered, for example, an IP packet, the OfficeConnect Gateway
parses each rule defined in the IP protocol section sequentially according to the
line number. Filtering is performed based on the first match that occurs. If there is
no match, the packet is accepted by default. For this reason, you should order
your protocol rules so that the rules you expect to be most frequently matched are
in the beginning of the section. This reduces the amount of parsing time that
occurs during filtering.
The following table describes each field used in the rule syntax:
Description
IP protocol data filter section
IP-RIP advertising section
Login Access filter section
Creating Filters
27-3
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