Specifications

Why Would I Use LSNAT in My Network?
September 8, 2010 Page 2 of 28
oftheserverfarmassociatedwiththeVIPaddress.Thepacketisthenforwardedtothe
selectedrealserver.
4. Therealserversendsaserviceresponsebacktotheclientwithitsaddressastheresponse
sourceaddress.
5. Attherouter,LSNATseestherealserveraddressandknowsitmust
firsttranslateitbackto
theVIPaddressbeforeforwardingthepacketontotheclient.
Figure 1 LSNAT Overview
Why Would I Use LSNAT in My Network?
Theneedforloadsharingariseswhenasingleserverisnotabletocopewiththedemandfor
multiplesessionssimultaneously.Legacyloadsharingschemeswereoftenad‐hocand
platform‐specific,havingtheproblemoflengthyreorderingtimesontheserversandtheinability
toaccountforserverload
variations.LSNATconfigurationandoperationisseparatefromthe
clientandserversandthereforedoesnotcarewhichclient,server,orserviceisinvolved.Itmerely
mapsasingleVI PtomultiplerealserverIPaddressandportcombinations,basedupona
configuredloadbalancingalgorithm,andforwardspacketsaccordingly.
With
loadsharingovermultipleservers,reliabilityisincreasedbyallowingyoutotakean
individualserverofflineforscheduledmaintenance,withoutdisruptingongoingservice
operations.Theserversareeasilyremovedandreplacedinthequeuemakingmaintenancea
transparentactivity,eliminatingmaintenancerelateddowntimeforthesite.
Loadsharingalso
providesredundancyinthecaseofaserverfailure.LSNATautomatically
removesthefailedserverfromtheselectionprocess.Whenthefailedserverbecomesactiveagain,
LSNATautomaticallyaddstheserverbackintotheselectionprocess.
Real Server
IP Address
Request VIP
to Real IP
Address
Translation
LSNAT
Configured
Virtual IP
Address
Server
Response
Packet
Response Real
IP to VIP
Address
Translation
Client
Real Server
IP Address
Real Server
IP Address
Real Server
IP Address
a
l
Global
Internet
ServerFarm
1
4
5
2
3
Router