3Com SUPERSTACK 2200, Руководство пользователя

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Creating Packet Filters 12-17
Combining All the Filters. Together, the four packet filters work to
perform the solution to the problem: filtering the broadcast packets from
the market data servers. These steps show how to create this filter:
1 Name the filter:
“Discard XNS & IP pkts w/in socket range”
2 Perform steps 2 through 4 as described in “Packet Filter One” on page 12-14.
3 Perform steps 2 through 8 as described in “Packet Filter Two” on page 12-15.
4 Add an and statement to compare the results of step 2 and the results of
step 3:
and # compare if XNS & in range
5 Perform steps 2 through 4 as described in “Combining a Subset of the
Filters” on page 12-16.
6 Add an or statement:
or # determine if the type field is either XNS or IP
7 Add a not statement to discard any matching packets:
not # discard if (IP & in range) & (XNS & in range)
The complete packet filter that discards IP and XNS packets that are within
the specified range is shown on page 12-13.
Tools for Writing
a Filter
You can create a new packet filter using either an ASCII-based text editor
(such as
EMACS or vi ) or the line editor built into the Administration
Console. Using an ASCII-based text editor allows you to create multiple
copies of the packet filter definition, which you can then copy onto one or
more Switch 2200 systems from a networked workstation. This method also
allows you to archive copies of filter definitions.
Using the Built-in Line Editor
The built-in text editor provides a minimal set of editing functions that you
can use to edit a packet filter definition one line at a time. A single line is
limited to no more than 79 characters. The number of lines is limited only
by available memory.