User`s guide

5-8
Filters
port filters are described in the next section.
The ATX allows you to implement up to 100 combination port
filters (total, for all connected ports). Combination port filters may
be logically linked to one another as described previously in the
AppleTalk example.
Each combination port filter generates statistics when invoked,
and thresholds can be set to trigger alarms to the NMS.
5.5.1 Configurable Fields
Each combination port filter may contain entries for all seven of
the configurable fields (with the exception that the entry port and
port/group match fields may only be included in an exit port
filter). If no value is specified for a particular field, that field will
not be used for that filter. The port field must always be specified,
since it identifies which traffic flow the ATX is to observe for
filtering. If only the port is specified, the filter will screen no
packets to or from that port (depending on whether it is an entry
(source port filter) or an exit (destination port filter), because none
of the filtering criteria fields were set.
The source address, destination address, protocol type, custom
mask, and source port fields may be defined as True, False, or Not
applicable. These definitions specify how the information in each
field is to be applied:
• True – Means all traffic that matches the field will be filtered.
• False – Means all traffic that does not match the field selection
will be filtered (inverse filter).
• Not applicable—Means that when the filter is invoked, the ATX
will not check for this field. (This is the default selection for each
field.)
In addition to the configurable fields, there are also two options
that you can use with all filters: