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Table Of Contents
VMware Server User’s Guide
250 VMware, Inc.
External Access from the NAT Network
Ingeneral,anyprotocolusingTCPorUDPcanbeusedautomaticallybyavirtual
machineontheNATnetworksolongasthevirtualmachineinitiatesthenetwork
connection.ThisistrueformostclientapplicationssuchasWebbrowsing,Telnet,
passivemodeFTP ,anddownloadingstreamingvideo.Additionalprotocol
supporthas
beenbuiltintotheNATdevicetoallowFTPandICMPecho(ping)toworkcompletely
transparentlythroughtheNAT.
Ontheexternalnetworktowhichthehostisconnected,anyvirtualmachineonthe
NATnetworkappearstobethehostitself,becauseitsnetworktrafficusesthe
host’sIP
address.ItisabletosendandreceivedatausingTCP/IPtoanymachinethatis
accessiblefromthehost.
Beforeanysuchcommunicationcanoccur,theNATdevicemustsetupamapping
betweenthevirtualmachine’saddressontheprivateNATnetworkandthehost’s
network
addressontheexternalnetwork.
Whenavirtualmachineinitiatesanetworkconnectionwithanothernetworkresource,
thismappingiscreatedautomatically.Theoperationisperfectlytransparenttotheuser
ofthevirtualmachineontheNATnetwork.Noadditionalworkneedstobedonetolet
thevirtualmachineaccess
theexternalnetwork.
Thesamecannotbesaidfornetworkconnectionsthatareinitiatedfromtheexternal
networktoavirtualmachineontheNATnetwork.
Whenamachineontheexternalnetworkattemptstoinitiateaconnectionwithavirtual
machineontheNATnetwork,itcannotreachthevirtual
machinebecausetheNAT
devicedoesnotforwardtherequest.Networkconnectionsthatareinitiatedfrom
outsidetheNATnetworkarenottransparent.
However,itispossibletoconfigureportforwardingmanuallyontheNATdeviceso
networktrafficdestinedforacertainportcanstillbeforwardedautomaticallyto
a
virtualmachineontheNATnetwork.Fordetails,seeAdvancedNATConfiguration”
onpage 251.
FilesharingofthetypeusedbyWindowsoperatingsystemsandSambaispossible
amongcomputersontheNATnetworkincludingvirtualmachinesandthehost
computer.IfyouareusingWINSserversonyour
network,avirtualmachineusing
NATnetworkingcanaccesssharedfilesandfoldersonthehostthatareknownbythe
WINSserversolongasthosesharedfilesandfoldersareinthesamew orkgroupor
domain.