User`s guide

5-14
Filters
• Monitoring traffic patterns as an aid in determining optimum
network design, usage policies, etc.
• Monitoring potential security threats.
• Evaluating security policies.
Values: either Yes (don’t filter the packet; just count the packet for
statistical purposes) or No (filter the packet if it meets the filtering
criteria). Yes is the default.
Linking Combination Port Filters
Multiple combination port filters may be logically linked using the
boolean and/or operators, as long as they apply to the same port
and filter type. By default, each combination port filter represents a
separate logical or test. That is, a packet will be filtered if the
conditions specified in any of the filters are present.
When two or more combination port filters must match, you can
use the And operator so the filters are linked with a logical And
instead of a logical Or. A packet then will be filtered only if the
conditions specified in both or all of the logically linked filters are
present.
Values: either Or (filter based on the options specified just within
this filter) or And (filter based on the options specified in this filter
and the next filter for the same Port and Type). Or is the default.
5.6 ADDING A FILTER
You can add filters for any port. Every filter has many possible
fields as described in the sections above. If all of the conditions in a
filter are present within a packet, then the packet is filtered.
You can also add pseudo filters to any port. Pseudo filters allow
you to gather statistics before you actually implement the filters.
You can then use the statistics for “what-if” traffic and usage
analysis.