Technicolor - Thomson 210i - Manual (Page 50)

SpeedTouch 210i
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IP Filter/Firewall Setup
The IP Filter/Firewall function helps to prevent your local network against attack from
outside. It also provides a method of restricting users on the local network from accessing
the Internet. Additionally, it can filter out specific packets to trigger the router to place an
outgoing connection.
An Overview of the Firewall
The IP Filter/Firewall includes two types of filter: Call Filter and Data Filter. The former is
designed to block or allow IP packets that will trigger the router to establish an outgoing
connection. The latter is designed to block or allow which kind of IP packets are allowed
to pass through the router when the WAN connection has been established. It works like
this: when an outgoing packet is routed to the WAN, the IP Filter will decide if the packet
should be forwarded to the Call Filter or Data Filter. If the WAN connection has not been
established, the packet will enter the Call Filter. If the packet is not allowed to trigger
router dialing, it will be dropped. Otherwise, it will initiate a call to establish the WAN
connection.
If the WAN connection of the router has been established, the packet will pass through the
Data Filter. Packets match the block rule will be dropped and the contrary will be sent to
the WAN interface. Alternatively, if an incoming packet enters from the WAN interface, it
will pass through the Data Filter directly. If the packets match the block rule, it will be
dropped. Otherwise, it will be sent to the internal LAN. The filter architecture is shown as
below.