Configuring Load Sharing Network Address Translation (LSNAT)
Enterasys Matrix DFE-Gold Series Configuration Guide 19-3
wouldonlyrequiretheuseofonebindinghardwareresource(insteadofoneperserviceper
client).
Inordertousestickypersistence,thefollowingconfigurationcriteriaarerequired:
•Stickypersistencemustbeconfiguredfortheserverfarmgroup(withthestickycommand)as
wellasforthevirtualserver(withthepersistencelevelcommand).
•Therealserversinthisserverfarmaretobeusedforallservices.Theserversarenotallowed
tobeusedwithotherserverfarmstosupportothervirtualserverservices.Thereisone
exceptiontothisrule,describedinthenextbulletitem.
•StickymeansallTCPportsorallUDPportsonthevirtualserveraresupported,butnotboth.
YoucancreatetwovirtualserverswithdifferentIPaddresses(oneforTCPprotocolsandone
forUDPprotocols/ports)andusethesamerealservers(withdifferentserverfarmnames).
ThatwayallTCPandUDPportsaresupportedbythesamesetofrealservers.
•Port0inthevirtualserverhastobeusedtosupportthisserviceandisreservedforthis
purpose.
•TheserviceFTPconfigurationisnotneededforthistypeofpersistence.(Seethevirtual
command,virtualonpage 1922.)

Configuring Direct Access to Real Servers

WhentheLSNATrouterhasbeenconfiguredwithloadbalancingserverfarmgroups,withreal
serversandvirtualserversconfiguredand“inservice,”therealserversareprotectedfromdirect
clientaccessforallservices.Loadsharingclientscanonlyaccessspecificservicesonthereal
serversbymeansofthevirtualserversconfiguredtoprovidethoseservices.
Ifyoualsowanttoprovidedirectclientaccesstorealserversconfiguredaspartofaserverfarm
group,therearetwomechanismsthatcanprovidedirectclientaccess.
Thefirstmechanism,configuredwithinvirtualserverconfigurationmodewiththeallow
accessserverscommand,allowsyoutoidentifyspecificclientswhocansetupconnections
directlytoarealserversIPaddress,aswellascontinuetousethevirtualserverIPaddress.
Thesecondmechanism,configuredinGlobalconfigurationmodewiththeipslballowaccess_all
command,allowsallclientstodirectlyaccessallservicesprovidedbyrealservers,exceptforthose
servicesconfiguredtobeaccessedbymeansofaconfiguredvirtualserver.Therealserversarestill
protectedfromdirectclientaccessforconfiguredservicesonly.Forexample,usingthis
mechanism,ifyouconfiguredaloadbalancingservergroupcontaining“realserver1”and
“realserver2”toprovideHTTPservicethroughvirtualserver“vserverhttp,”clientscanonly
accesstheHTTPserviceonthoserealserversbymeansofthe“vserverhttp”virtualserver.
However,clientscandirectlyaccess“realserver1”and“realserver2”foranyservicesotherthan
HTTP.
Ifyoucombinethetwomechanisms,thatis,configureipslballowaccess_allattheGlobal
configurationmodeandalsoconfigureallowaccessserverswithinavirtualserversconfiguration
mode,theclientsidentifiedwiththeallowaccessserverscommandwillhavedirectaccesstothe
realserversforallservices(includingthoseprovidedbyavirtualserver)andbeblockedfrom
usingthevirtualserver.Soforexample,an“allowed”clientcanaccess“realserver1”and
“realserver2”directlyforallservices,includingHTTP,butcannotaccessthoseserversforHTTP
bymeansofthe“vserverhttp”virtualserver.

Service Verification

UPDportserviceverificationcanbeenabledononeormoreloadbalancingservers.Thefirmware
accomplishesthisbysendingaUDPpacketwith“\r\n”(CarriageReturn/LineFeed)asdatato