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LanScaper
TM
(ARP)requestdirectedtoitsproposedMyIPaddress.AresponsetotheARPtellsthetesterthat
someotherdeviceontheLANisalreadyusingthatIPaddress.TheDHCPprotocolspecification
(RFC1541)saysthatinthecaseaserveroffersanaddressalreadyinuse,thereceiverofthat
addressshouldrejectitandrequestanother.TheLanScaper™doesnotinformtheserveraboutthe
conflict,butitdoesreportontheLCD“MyIPinuseonthisnetwork”.Ifthisisfound,thetester
willnotcontinueintothePINGstate,asusinganotherdevice'sIPaddressisnotpermissibleona
LAN.Thisconditionsh
owsthattheDHCPserverismis-configuredasitshouldreserveallIP
addressesalreadyinuseontheLAN.Thetesterwillrestartfromthisstateautomaticallyafterone
minute,orcanbemanuallyrestartedtoretrythetest.Ifmultipleretriesallendupunsuccessful,the
testermustbemanuallyconfiguredandusedintheDHCPOffmode.Inthiscase,theLAN
configurationparameterscanbeseeninSetupmodeintheLastDHCPsub-menu,includingtheIP
addressofferedtothetester,thevalueofMyIP.
AftersuccessfullyreceivingavalidIPaddress,theoperationofthetestercontinueswithth
ePING
statedescribedbelow.
-ThetesterutilizesthemanuallyenteredPINGSetupinformation.To
determinetheIPparameterconfigurationoftheLAN,theconfigurationofanotherdeviceonthat
LANmustbechecked.OnaWindowsPC,thecommand“ipconfig”canbeusedtodeterminethe
IPaddresses,Netmask,andDefaultGateway(Router)beingused.OnaLinuxcomputer,thesame
informationcanbefoundusingthe“ifconfig”and“route”commands.TheNetmaskandRouter
informationcanbeenteredjustasdisplayedonthePC.ThevalueenteredforMyIPmustbe
similar,butnotidenticaltothePC'
sIPaddress.TheNetmaskdefinestheaddressesthatmustbe
commonbetweenthePCandthetesterforittobepossibleforthemtocommunicatedirectlyonthe
sameLANsegment.AgoodguessistouseanIPaddressdifferentbyjustafewlow-orderdigitsin
thelow-orderbyteoftheIPaddress.Onceallthemanualparametersaresetup,thePINGtestcan
bestartedbypressingtheNTWRKbuttontwice,andthentheSELbutton.Onceanactivelinkis
found,thevalueenteredforMyIPischeckedforconflict.ThetesterissuesanARPrequestdirected
toitsproposedMyIPaddress.AresponsetotheARPtellsthe
testerthatsomeotherdeviceonthe
LANisalreadyusingthatIPaddress,anditreports“MyIPinuseonthisnetwork.”.The
LanScaper™willnotcontinuethePINGtest,asusinganotherdevice'sIPaddressisnot
permissibleonaLAN.Thetesterwillrestartfromthisstateautomaticallyafteroneminute,butthe
valueenteredforMyIPmustbemanuallychangedtotryadifferentIPaddresstopreventconflict.
-OnceMyIPhasbeenverifiedasavailable,ineitherDHCPOnorOffmodes,thenext
stepistoentertheactivePINGconversationstate.ThetesterLCDdisplaysthePINGStatus
screen,“Tg1-4
”(unlessdisabled),“Rtr”and“DNS”(ifDHCPOn)acronymsonthetoplineofthe
LCD,anddirectlyundertheassociatedacronym,thestatusofeachPINGconversation.Acursor
()isshownonthetoplinethatcanbemovedwiththeleft/rightarrowbuttonstoselectanyofthe
conversations.PressingtheSELbuttonwillpushdownintomoredetailaboutthatconversation.
ThefirstpressofSELwilldisplaythevalueofMyIPcurrentlyinuse.AsecondpressofSEL(or
delayofthreeseconds)willdropintothesecondpageofstatus.AthirdpressofSEL(orafter10
seconds)willdropintoathirdpageofst
atus,ifavailable,orreturntothemainPINGdisplay.Ifthe
thirdpageisdisplayed,afinalpressofSEL(orafteranother10seconds)willreturntothemain
PINGdisplay.
ThefirststepinestablishingtheconversationsistoattempttolocatetheRouterontheLAN
segment.TheLanScaper™doesthisusingtheAddressResolutionProtocol(ARP).
DHCPOff(Manual)Mode
PINGState