Avaya, Inc. - 193 - PARTNER ACS 1600 DSL module User Guide
E. IP Filtering
The following assumes that you have a working knowledge of
IP protocols.
Filtering executes on the WAN port that you select. There are
two different sets of filters and each filter maintains its own
statistics:
Input - Input packets are filtered after the network
address translation.
Output - Output packets are filtered before the network
address translation.
The maximum total number of filters is 128.
Packets pass through the appropriate set of filters in the order
in which the filters display in the list shown on the user
interface (Configure IP Router > Configure IP Filtering >
Display all filters of the chosen type). Each packet moves
down the list of filters until it reaches the end or the attributes
of an active filter match the packet.
When a "match" occurs, the packet is the n processed
according to the action field (Pass or Discard) of the first filter
that matched the packet:
Pass - packet passed to the next level.
Discard - packet discarded. When output packets are
dropped, RTCS_OK is returned from IP_route.
When you create a new filter, all fields are s et to an inactive
state. An inactive filter passes all IP packets - you must
modify at least one field to narrow the range of packets to
pass or change the action to discard all packets.
To create a set of filters to pass only certain types of packets,
you need to create a default filter that discards all packets and
then insert narrower filters before the default filter. For
example, you need to add a filter to cover each range of
packets.
If you want to select only the packet ranges to discard, then
there is no default filter needed, because the default action is
to pass all packets. You only have to add filters that set the
range to discard and set the actions of those filters to discard.
The order of the filters matters if you are mixing filters with
different actions or if you want the overlapping filters to display
accurate statistics.