Specifications

September 8, 2010 Page 1 of 28
Configuring Load Sharing
Network Address Translation (LSNAT)
Thisdocumentprovidesthe followinginformationaboutconfiguringLSNATontheEnterasys
Matrix
®
N‐SeriesandtheEnterasysS‐Series
®
platforms.
What is LSNAT?
LSNATisaloadbalancingroutingfeature.Itprovidesloadsharingbetweenmultipleservers
groupedintoserverfarmsthatcanbetailoredtoanindividualserviceorallservices,without
requiringanymodificationtoclientsorservers.Examplesofwell‐knownservicesareHTTPon
port80,SMTP(e‐mail)on
port25,orFTPonport21.LSNATisdefinedinRFC2391.
TherearethreeLSNATconfigurationcomponents:
•Theclientthatisrequestingaservicefromtheserver
•Thevirtualserver,configuredontheLSNATrouter,thatinterceptstheservicerequestand
determinesthephysical(real)servertherequestwill
beforwardedto
•Theserverfarmthatisalog ical entity containingthemultiplerealservers,oneofwhichwill
servicetheclient’srequest
Figure 1onpage 2providesthefollowingexampleofanLSNATdeployment:
1. Arequestforserviceissentbytheclienttotheserverfarm.
2. Thedestinationaddressfor
theservicerequestisthevirtualserverʹsuniqueVirtualIP(VIP)
address.AVIPaddresscanbeanIPaddressoranIPaddressandportaddresscombination.
ThesameIPaddresscanbeusedformultiplevirtualserversifadifferentportaddressisused.
TheLSNATconfiguredrouter
recognizestheVIPaddressandknowsthatLSNATmustselect
arealservertoforwardtherequestto.
3. Beforeforwardingtherequest,basedupontheserverloadbalancingprocessconfigured
(roundrobinisdisplayed),LSNATselectstherealserverforthisrequest.LSNATchangesthe
destinationIPaddressfromthe
VIPaddresstotheaddressoftheselectedrealservermember
For information about... Refer to page...
What is LSNAT? 1
Why Would I Use LSNAT in My Network? 2
How Can I Implement LSNAT? 3
LSNAT Overview 4
Configuring LSNAT 10
LSNAT Configuration Example 16
Terms and Definitions 25