Specifications

LSNAT Overview
September 8, 2010 Page 9 of 28
addressthatreturnstrafficbackthroughtheLSNATrouter.SincetheclientIPaddressesare
usuallyunknowntotherealserver,mostrealserversendupsettingtheirdefaultroutertothe
LSNATrouter.IftheLSNATrouterisnotconfiguredasthedefaultrouter,theLSNATrouterand
realserver
mustbelocatedsomewhereinthenetworktopologythatguaranteesthatreturntraffic
flowsthroughtheLSNATrouter.
Ifinstead,theclientIPaddressisNATed,thisallowstherealserverstobelocatedanywhereina
network,sincethepacketsfromroutertoreal‐serverwillbesourceNATedwith
anIPaddress
ownedbytherouteritself.
UsethesourcenatpoolcommandtospecifyaNATpooltouseforsourceNATing.TheNATpool
isusedinanoverloadmode.
The FTP Control Port
TheFTPportassignmentdefaultstoport21.Youcangloballyassignanon‐stan dardFTPcontrol
portinglobalconfigurat ionmodethatwillbeusedbyallvirtualservers.
The Virtual Server Virtual Port and Real Server Port
Whenconfiguringavirtualserverandrealserver,theportmustbeconfiguredforaprotocoltype
andportvalue.Thissectionspecifiesportprotocolandportvalueconsiderationstotakeinto
accountwhenconfiguringavirtualserverorrealserver.
Virtual Server Virtual Port
Theconfigurationofthevirtualservervirtualporthastwomeaningsdependinguponwhether
theporthasazeroornon‐zerovalue:
•Ifanon‐zerovalueisset,thenincomingpackets’destinationportsarematchedtothatport.
•Ifazerovalueisset,thentheincomingpackets’destination
portswillonlymatchthatvirtual
serverifthereisnonon‐zeroportmatchwithanothervirtualserver.Inthiscasethezeroport
isacatchallthatmeansmatchanyport.
Thevirtualservervirtualportprotocol(UDP/TCP)mustalwaysmatchtherealserverport
protocol.
Thevirtualserver
isidentifiedbyitsVirtualIPAddress(VIP),portprotocol,andportnumber.A
virtualserverconfiguredforagivenVIPandportnumbermustbeconfiguredforeitherUDPor
TCP,butcannotbeconfiguredforboth.
Real Server Port
Theconfigurationoftherealserverporthastwomeanings:
•Ifanon‐zerovalueissettotherealserverport,thenanybindingscreatedusingthatreal
serverwillusetherealserver’sdestinationport. 
•Ifazerovalueissettotherealserverport,thenanybindings
createdusingthatrealserver
willusetheclient’soriginaldestinationport.
Iftherealserver’sportissetto0,theonlyvalidfaildetecttypesfortherealserverisnoneor
ping.