Knowledgebase: Firewall / Security
What is the Difference between Call Filter and Data Filter?
Posted by Roy Panetta on 14 December 2011 11:00 AM

Vigor routers have a user-configurable IP filter (Call Filter/ Data Filter). This is in “Firewall>>General Setup” configuration menu. The default filters block NetBios traffic.

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IP filter architecture categorizes traffic into two types: Call Filter and Data Filter. This is based on whether the Internet connection is up or down (WAN link status is up or down).

Call Filter – applies when there is no existing Internet connection.The Call Filter is applied to all outgoing traffic. It will check packets according to the filter rules. If legal, the packet will be allowed to pass. Then the router shall “initiate a call” to start the Internet connection and send the packet out to Internet.

Data Filter – applies when there is an existing Internet connection. The Data Filter is applied to incoming and outgoing traffic. It will check packets according to the filter rules. If legal, the packet will be allowed to pass through the router.

The following illustrations are flow charts explaining how router will treat incoming traffic and outgoing traffic respectively.

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