Filter Priority; How Individual Filters Work - Netopia 2200 series Software User's Manual

For 2200 and 3300 series gateways
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Filter priority

packet
first
filter
match?
yes
forward
discard?
forward
to network
before that packet ever reaches any of the other filters. If the first filter can neither forward
nor discard the packet (because it cannot match any criteria), the second filter has a
chance to forward or reject it, and so on. Because of this hierarchical structure, each filter
is said to have a priority. The first filter has the highest priority, and the last filter has the
lowest priority.
How individual filters work
As described above, a filter applies criteria to an IP packet and then takes one of three
actions:
Forwards the packet to the local or remote network
Blocks (discards) the packet
Ignores the packet
A filter forwards or blocks a packet only if it finds a match after applying its criteria. When
no match occurs, the filter ignores the packet.
156
Continuing the customs inspectors analogy, imagine the
inspectors lined up to examine a package. If the package
matches the first inspector's criteria, the package is either
rejected or passed on to its destination, depending on the
first inspector's particular orders. In this case, the package
is never seen by the remaining inspectors.
no
If the package does not match the first inspector's criteria,
send
it goes to the second inspector, and so on. You can see that
to next
the order of the inspectors in the line is very important.
filter
For example, let's say the first inspector's orders are to
send along all packages that come from Rome, and the sec-
ond inspector's orders are to reject all packages that come
from France. If a package arrives from Rome, the first
or
inspector sends it along without allowing the second inspec-
discard
tor to see it. A package from Paris is ignored by the first
(delete)
inspector, rejected by the second inspector, and never seen
by the others. A package from London is ignored by the first
two inspectors, so it's seen by the third inspector.
In the same way, filter sets apply their filters in a particular
order. The first filter applied can forward or discard a packet

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This manual is also suitable for:

3300 series33423356Firmware version 7.6

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