2.5

Table Of Contents
VMware Lab Manager User’s Guide
186 VMware, Inc.
Why Should I Fence Configurations?
Typically,youwanttoenablenetworkfencingunderthesecircumstances:
Youhaveaconfigurationwithoneormoreservers,andyouanticipatecloningthe
configurationnumeroustimes.
Youhaveaconfigurationinvolvingadifficultandcomplexsetup,andcloningthe
configurationisaneasierroutethanrepeatingthesetup.
Withfencing,engineerscanrunmultiple,independenttestsonaconfiguration
deployedmultipletimes.Fencingisparticularlyusefulwhenadeveloperneedsto
examineabugwithoutinterruptingor
stoppingongoingtestingonaconfiguration.
Lab Manageralsoenablesyoutoreproducethebugatalatertimeifthedeveloperis
unavailable.
ThedefaultnumberofconcurrentlydeployedfencedconfigurationsonaManaged
Serversystemis20.Ifyouneedmoreconfigurations,youcanincreasethenumber
withoutanypenalty.
From
aperformanceperspective,networkfencingimpactsthetrafficflowbetween
modules.FencingrequiresaslightlyhighernumberofresourcesontheManaged
Serversystem,suchasmemory,CPU,networking,andvirtualmachineslots.Ifyou
enablefencingbutneveruseit,theseresourcesdonotcomeintoplay.
How Does Fencing Work?
Virtualmachinesinaconfigurationhavepreconfigured(internal)IPaddresses.When
youdeployvirtualmachinesinfencedmode,Lab Managerassignsauniqueexternal
IPaddresstoeachofthesemachines.Throughtheseexternaladdresses,virtual
machinesbothinsideandoutsidethefencecancommunicatewitheachother.
Lab Managerusesavirtual
routertoroutepacketsbetweenthesevirtualmachines.
Lab Managerconfiguresthevirtualrouterwhenyoudeployafencedconfiguration
anddeletesitwhenyouundeploytheconfiguration.
N
OTEWhenyoudeployaconfigurationinfencedmodewiththeBlockTrafficInand
Outoption,Lab ManagerdoesnotcreateavirtualrouterorassignexternalIP
addresses.See“FencingOptions”onpage 188.