Specifications

Configuring Load Sharing Network Address Translation (LSNAT)
Enterasys Matrix N Standalone (NSA) Series Configuration Guide 19-3
wouldonlyrequiretheuseofonebindinghardwareresource(insteadofoneperserviceper
client).
Inordertousestickypersistence,thefollowingconfigurationcriteriaarerequired:
•Stickypersistencemustbeconfiguredfortheserverfarmgroup(withthestickycommand)as
wellasforthevirtualserver(withthe
persistencelevelcommand).
•Therealserversinthisserverfarmaretobeusedforallservices.Theserversarenotallowed
tobeusedwithotherserverfarmstosupportothervirtualserverservices.Thereisone
exceptiontothisrule,describedinthenextbulletitem.
•Stickymeansall
TCPportsorallUDPportsonthevirtualserveraresupported,butnotboth.
YoucancreatetwovirtualserverswithdifferentIPaddresses(oneforTCPprotocolsandone
forUDPprotocols/ports)andusethesamerealservers(withdifferentserverfarmnames).
ThatwayallTCPandUDPports
aresupportedbythesamesetofrealservers.
•Port0inthevirtualserverhastobeusedtosupportthisserviceandisreservedforthis
purpose.
•TheserviceFTPconfigurationisnotneededforthistypeofpersistence.(Seethevirtual
command,“virtual”onpage 19‐22.)
Configuring Direct Access to Real Servers
WhentheLSNATrouterhasbeenconfiguredwithloadbalancingserverfarmgroups,withreal
serversandvirtualserversconfiguredand“inservice,”therealserversareprotectedfromdirect
clientaccessforallservices.Loadsharingclientscanonlyaccessspecificservicesonthereal
serversbymeansofthe
virtualserversconfiguredtoprovidethoseservices.
Ifyoualsowanttoprovidedirectclientaccesstorealserversconfiguredaspartofaserverfarm
group,therearetwomechanismsthatcanprovidedirectclientaccess.
Thefirstmechanism,configuredwithinvirtualserverconfigurationmodewiththeallow
accessserverscommand,
allowsyoutoidentifyspecificclientswhocansetupconnections
directlytoarealserver’sIPaddress,aswellascontinuetousethevirtualserverIPaddress.
Thesecondmechanism,configuredinGlobalconfigurationmodewiththeipslballowaccess_all
command,allowsallclientstodirectlyaccessallservices
providedbyrealservers,exceptforthose
servicesconfiguredtobeaccessedbymeansofaconfiguredvirtualserver.Therealserversarestill
protectedfromdirectclientaccessforconfiguredservicesonly.Forexample,usingthis
mechanism,ifyouconfiguredaloadbalancingservergroupcontaining“realserver1”and
“realserver2”
toprovideHTTPservicethroughvirtualserver“vserver‐http,”clientscanonly
accesstheHTTPserviceonthoserealserversbymeansofthe“vserver‐http”virtualserver.
However,clientscandirectlyaccess“realserver1”and“realserver2”foranyservicesotherthan
HTTP.
Ifyoucombinethetwomechanisms,thatis,configure
ipslballowaccess_allattheGlobal
configurationmodeandalsoconfigureallowaccessserverswithinavirtualserver’sconfiguration
mode,theclientsidentifiedwiththeallowaccessserverscommandwillhavedirectaccesstothe
realserversforallservices(includingthoseprovidedbyavirtualserver)andbeblockedfrom
using
thevirtualserver.Soforexample,an“allowed”clientcanaccess“realserver1”and
“realserver2”directlyforallservices,includingHTTP,butcannotaccessthoseserversforHTTP
bymeansofthe“vserver‐http”virtualserver.
Service Verification
UPDportserviceverificationcanbeenabledononeormoreloadbalancingservers.Thefirmware
accomplishesthisbysendingaUDPpacketwith“\r\n”(CarriageReturn/LineFeed)asdatato