Specifications

LSNAT Overview
September 8, 2010 Page 5 of 28
Figure 2 LSNAT Packet Flow
The Server Farm
Theserverfarmisalogicalentitymadeupofmultiplerealservers.Youconfigureaserverfarmby
namingitandpopulatingitwithrealservermembers.Eachserverfarmisassociatedwitha
virtualserverthatisconfiguredwithauniqueVirtualIP(VIP)address.Youcanconfigure
multiple
serverfarmsforasinglerouter,buteachserverfarmmustbeassociatedwithaunique
virtualserver.Eachserverfarmisconfiguredtousealoadbalancingalgorithm.Theload
balancingalgorithmdeterminestherealserverselectionprocessforthisserverfarm.Theserver
farmdefaultstoaround
robinloadbalancingalgorithm.
Server Selection Process
Theserverselectionprocessdeterminesthemannerinwhicharealserverwillbeselectedforthis
session.Theserverselectionprocessisoneofthreeconfig urableloadbalancingalgorithms,also
referredtoaspredictors:roundrobin,weightedroundrobin,andleastconnections.
Round Robin
Theroundrobinalgorithmtreatsallserversequallybyorderingtheserversandselectingthem
oneatatimeforeachnewsessionrequest.Whenitgetstothelastrealserverintheordering,it
startsatthebeginningagain.
Weighted Round Robin
Weightedroundrobinisaroundrobinalgorithmthattakesintoaccountaweightassignedtoeach
realserver.Weightisawayofaccountingfortheresourcedifferencesbetweenservers.Ifaserver
hasthecapacitytohandletwicethe numberofsessionsasanotherserver,itsweightratioto
the
otherservercanbesetto2:1.Thedefaultweightforallrealserversis1.Whenallrealserversare
10.10.125.1:80
10.10.125.2:80
10.10.125.3:80
10.10.125.4:80
DA 196.86. 100.12:125
SA 194.56. 13.2:80
Client
IP196.86.100.12:125
VIP194.56.13.2:80
Global
Internet
ServerFarm1
Router
DA 10.10. 125.1:80
SA 196.86. 100.12:125
DA 194.56. 13.2:80
SA 196.86. 100.12:125
DA 194.56. 13.2:80
SA 10.10. 125.1:80