User Manual

40D-Link DSL-520B ADSL2+ Modem User Manual
Section 7 - Device Info
Usingportforwarding(theforwardingofrequeststoparticularports),therouterisforcedtosendrequestsfromtheInternet
foracertainservice,forexample,agame,totheappropriateport(s)onthePConwhichthegameisrunning.Porttriggering
isaspecialvariantofportforwarding.Unlikeportforwarding,theDSLrouterforwardsthedatafromtheportblocktothePC
which has previously sent data to the Internet via a certain port (trigger port). This means that approval for the data transfer
isnottiedtoonespecicPCinthenetwork,butrathertotheportnumbersoftherequiredInternetservice.
Wherecongurationisconcerned,youmustdeneaso-calledtriggerportfortheapplicationandalsotheprotocol(TCPor
UDP) that this port uses. You then assign the public ports that are to be opened for the application to this trigger port. The
router checks all outgoing data for the port number and protocol. If it identies a match of port and protocol for a dened
triggerport,thenitopenstheassignedpublicportsandnotestheIPaddressofthePCthatsentthedata.Ifdatacomesback
fromtheInternetviaoneofthesepublicports,therouterallowsittopassthroughanddirectsittotheappropriatePC.Atrigger
eventalwayscomesfromaPCwithinthelocalnetwork.Ifatriggerportisaddressedfromoutside,theroutersimplyignoresit.
Note:
• Anapplicationthatisconguredforporttriggeringcanonlyberunbyoneuserinthelocalnetworkatatime.
• Afterpublicportsareopened,theycanbeusedbyunauthorizedpersonstogainaccesstoaPCinthelocalnetwork.
• WhentheDSLrouterissupplied,theNATfunctionisactivated.Forexample,allIPaddressesofPCsinthelocalnetworkareconverted
to the public IP address of the router when accessing the Internet. You can use NAT settings to congure the DSL router to carry out
the following tasks.
• Forfunctionsdescribedasfollows,IPaddressesofthePCsmustremainunchanged.IftheIPaddressesofthePCsareassignedvia
theDHCPserveroftheDSLrouter,youmustdisableDHCPserverasthesettingsinthelocalnetworkmenuentryfortheleasetime
orassignstaticIPaddressesforthePCs.
• YoucanenableordisabletheNATfunction.Bydefault,theNATfunctionisenabled.