Test-Um NT750 Network Card User Manual


 
LanScaper
TM
(ARP)requestdirectedtoitsproposedMyIPaddress.AresponsetotheARPtellsthetesterthat
someotherdeviceontheLANisalreadyusingthatIPaddress.TheDHCPprotocolspecification
(RFC1541)saysthatinthecaseaserveroffersanaddressalreadyinuse,thereceiverofthat
addressshouldrejectitandrequestanother.TheLanScaperdoesnotinformtheserveraboutthe
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“ipconfigcanbeusedtodeterminethe
IPaddresses,Netmask,andDefaultGateway(Router)beingused.OnaLinuxcomputer,thesame
informationcanbefoundusingthe“ifconfigand“routecommands.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
LanScaperwillnotcontinuethePINGtest,asusinganotherdevice'sIPaddressisnot
permissibleonaLAN.Thetesterwillrestartfromthisstateautomaticallyafteroneminute,butthe
valueenteredforMyIPmustbemanuallychangedtotryadifferentIPaddresstopreventconflict.
-OnceMyIPhasbeenverifiedasavailable,ineitherDHCPOnorOffmodes,thenext
stepistoentertheactivePINGconversationstate.ThetesterLCDdisplaysthePINGStatus
screen,“Tg1-4
(unlessdisabled),“Rtrand“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.TheLanScaperdoesthisusingtheAddressResolutionProtocol(ARP).
DHCPOff(Manual)Mode
PINGState