Справочное Руководство для Netopia 430 s

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Netopia ISDN Router Reference Guide
Input and output filters—source and destination
There are two kinds of filters you can add to a filter set: input and 
output. Input filters check packets received from the Internet, 
destined for your network. Output filters check packets transmitted 
from your network to the Internet.
Packets in the Netopia ISDN Router pass through an input filter if they originate 
in the WAN and through an output filter if they’re being sent out to the WAN.
The process for adding input and output filters is exactly the same. 
The main difference between the two involves their reference to 
source and destination. From the perspective of an input filter, your 
local network is the destination of the packets it checks, and the 
remote network is their source. From the perspective of an output 
filter, your local network is the source of the packets, and the remote 
network is their destination.
The Netopia ISDN Router
input filter
output filter
LAN
WAN
packet
packet
Type of filter
“source” means
“destination” means
Input filter
the remote network
the local network
Output filter
the local network
the remote network