Netopia d3100-i ユーザーズマニュアル

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 par ticular orders. In this case, the package is never seen by the remaining 
inspectors.

If the package does not match the first inspector’s criteria, it goes to the second inspector, and so on. You can 
see that the order of the inspectors in the line is ver y impor tant.

For example, let’s say the first inspector’s orders are to send along all packages that come from Rome, and the 
second inspector’s orders are to reject all packages that come from France. If a package arrives from Rome, 
the first inspector sends it along without allowing the second inspector to see it. A package from Paris is 
ignored by the first 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 par ticular order. The first filter applied can pass or discard a 
packet before that packet ever reaches any of the other filters. If the first filter can neither pass nor discard the 
packet (because it cannot match any criteria), the second filter has a chance to pass 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.

packet

first
filter

match?

yes

pass or
discard?

to network

discard
(delete)

pass

no

to next
filter

send