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LSB4 Reference Manual Filter Commands
6-1
If a filter list con-
tains more than six
or seven items, slow
performance may
result.
One filter list may
be associated with
one or all ports.
Introduction
Filters are used to permit or deny passage of data packets through the LSB4. The
Set Filter and Define Filter commands are used to specify filters. Also included
in this chapter are the associated commands Show/List Filter and Clear/Purge
Filter .
Filter commands define filters for different types of data packets, different pro-
tocols, and different patterns of data within packets. The filter is then configured
to either permit or deny passage through the LSB4.
When a filter is identified with a filter command, it is placed on a list stored in
the LSB4. In order to activate the filters, a filter list must be associated with a par-
ticular LSB4 port. Filter lists are associated with the different LSB4 ports using
the
Set/Define Switch command.
The LSB4 compares each data packet against each filter starting with the first fil-
ter on the list (up to 16 entries may be included in a filter list.) It continues com-
paring until the data packet matches a filter on the list. The packet will then be
either permitted or denied passage through the switch. If no match is found, the
packet is forwarded through the switch.
The order that filter commands are entered into the list is very important; switch-
ing the positions of two filters can have very different effects. For example, if a
filter list is ordered in the following manner:
♦
Allow all IP email traffic
♦
Deny all IP traffic
only IP email traffic will be forwarded. If the order of the filter list is reversed, as
displayed below:
♦
Deny all IP traffic
♦
Allow all IP email traffic
any IP packet traffic (including IP email packets) will not be forwarded, as the
processing of IP traffic stops at the first match on the filter list.
6chapternumber
For an explanation
of the
Set/Define
and Show/List
commands, see page
2-1.