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Survey the Network
4-8 Design Planning
authenticatedtothenetworkandinteractwithEnterasysNACforauthentication,assessment,
authorization,andremediation.Notehowever,thatthisconfigurationmaynotbepossibleif
trustedusersarealsobeingMACauthenticatedtothenetworkinthesameSecurityDomain.
Inthiscase,MACoruseroverrideswouldneedtobe
configuredforthetrustedusers,andthe
defaultNACconfigurationoftheSecurityDomainwouldspecifytheNACimplementation
forguestusers.
•Ifguestaccess isimplementedwithwebbasedauthenticationusingtheguestnetworking
featureonEnterasyspolicycapableswitches(supplyingdefaultcredentialsintheweblogin
pageforguest
users),theguestnetworkingfeaturemustbeconfiguredtosendthedefault
credentialstoabackendRADIUS serverandnotlocallyauthenticatethem.Thisisbecausein
theoutofbandNACconfiguration,theNACGatewaymustreceivetheauthentication
attemptviaRADIUSinordertodetecttheconnectingend
systems.ARADIUSserverwith the
guestnetworkingcredentialsmustbedeployedonthenetworksotheNACGatewaycan
proxytheRADIUSrequeststotheupstreamRADIUSserver.IfaRADIUSFilterIDorVLAN
Tunnelattributeisnotconfiguredfortheguestnetworkingcredentialsontheupstream
RADIUSserver,
EnterasysNACcanbeconfiguredtoincludeaFilterIDorVLANTunnel
attributeintheRADIUSAccessAcceptpacketreturnedtotheswitchbyimplementingauser
overridefortheguestnetworkingusername.
3. Identify the Strategic Point for End-System Authorization
Inthisstep,youwillidentifythestrategicpointinthenetworkwhereendsystemauthorization
shouldbeimplemented.
Themostsecureplaceforimplementingauthorizationisdirectlyatthepointofconnectionatthe
edgeofthenetwork,assupportedbyEnterasyspolicycapableswitches.Inthisconfiguration,the
implementation
ofoutofbandNACusingtheNACGatewayapplianceleveragespolicyon
Enterasysswitchestosecurelyauthorizeconnectingendsystems.
RFC3580capableswitchescanbeusedforauthenticationandauthorizationbyassigningend
systemstoparticularVLANsbasedontheauthenticationandassessmentresults.However,thisis
not
assecureasusingEnterasyspolicycapableswitches,forthetwofollowingreasons:
•VLANsauthorizeendsystemsbyplacingthemintothesamecontainer,withthetraffic
enforcementpointimplementedattheingress/egresspointtotheVLANontheVLANʹs
routedinterface.Be causeauthorizationisnotimplementedbetweenendsystems
withinthe
sameVLAN,anendsystem inaVLANisopentolaunchattacksorbeattackedbyother
deviceswithinthesameVLAN.Forexample,ifendsystemAwithvirusXandendsystemB
withvirusYarequarantinedintothesameVLAN,thenendsystemA
andBmaybecome
infectedwithvirusXandY.Enterasyspolicyuniquelyauthorizesconnectingendsystems
independentoftheirVLANassignmentbypermitting,denying,andprioritizingtrafficon
ingresstothenetworkattheportlevel.
•BecauseRFC3580capableswitchesimplementthetrafficenforcementpointforaVLANat
theVLAN’sroutedinterface,malicioustrafficisallowedontothenetworkandmayconsume
bandwidth,memory,andCPUcyclesoninfrastructuredevicesbeforebeingdiscarded
possiblyseveralhopsdeepwithinthenetwork.Thisisespeciallydetrimentaltotheoperation
ofthenetworkifasingleinterswitchlinkconnectingthe
accesslayertodistributionlayeris
usedtotransmittrafficfromboththequarantineVLANandtheproductionVLAN(suchasan
802.1QVLANtrunkedlink).Trafficfromquarantinedendsystems(forexample,worms
scanningforvulnerablehosts)canconsumetheentirebandwidthavailableontheinterswitch
linkandaffect
networkconnectivityforendsystemsontheproductionVLAN.Incontrast,
sincethetrafficenforcementpointforEnterasyspolicyisattheportofconnection,malicious
trafficneveringressesthenetworktocauseanydisruptiontonetworkconnectivity.
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