Installation guide

Features
1-4 Introduction
PoE (Power over Ethernet) Support
TheG3G124‐24Pswitchis802.3afcompliantout‐of‐box.TheG3G124‐24andtheG3G‐24TXIOM
canbeequippedwithuser‐installedoptionalPoEmodulestomakethem802.3afcompliant.For
moreinformationaboutinstallingoptionalPoEmodules,see“InstallinganOptionalPoEModule
ontheG3G‐24TX
IOM”onpage 2‐10and“InstallinganOptionalPoEModuleintheG3G124‐24
Switch”onpage 2‐23.
TheG3GswitchesandIOMsthatare802.3afcompliantprovidePoweroverEthernetcable
connectionsfromtheirRJ45frontpanelconnectorstopowereddevices(PDs)inthenetwork.
PoweroverEthernet(PoE)
referstotheabilitytoprovide48Vdcpowertoapowereddeviceusing
thesameEthernetcablingthatprovidesdata.ModernEthernetimplementationsemploy
differentialsignalsovertwistedpaircables.Thisrequiresaminimumoftwotwistedpairsfora
singlephysicallink.Bothendsofthecableare
isolatedwithtransformersblockinganyDCor
commonmodevoltageonthesignalpair.PoEexploitsthisfactbyusingtwotwistedpairsasthe
twoconductorstosupplyadirectcurrent.Onepaircarriesthepowersupplycurrentandtheother
pairprovidesapathforthereturncurrent.While
severalproprietarylegacyimplementationsof
PoEhavebeendeployedbyLANequipmentvendors,in2003theIEEEpublishedtheIEEE802.3af
specification,whichispartofthe802.3suiteofstandards.
TheswitchisfullycompliantwiththeIEEE802.3afstandard.Itsupportsthestandardresistor‐
baseddetectionmethod,aswell
asACdisconnectcapability. Theswitchisalsocapableof
supplying15.4wattsofpowerto96portsinnonredundantpowermode,and9.4wattsofpowerto
96portsinredundantpowermode.
Powered Device Classifications (PDs)
PDsaredevicesthatreceivetheiroperating48VdcpowerthroughaneworexistingEthernet
cablefromaswitchorotherdevicethatcanprovideaPoE‐compliantportconnection.This
enablesthePDtooperateinalocationwithoutlocalpower.Forexample:
• DevicessuchasPoE‐compliantremote
EXITsignsandPersonalDataAssistants(PDAs),
• DevicesthatsupportVoiceoverIPsuchasPoE‐compliantdigitaltelephones,
• DevicesthatsupportWirelessApplicationProtocol(WAP)suchassecuritycameras,laptop
PCs,andmanymoredevices.
Fan Management
TheG3systemsupportsthreegroupsofindependentlycontrollablefansandseveralfirmware
readablethermalsensors.Fanzonesareasfollows:
•Group1(fans1,2,and3)islocatedinthefrontleftoftheswitchtocooltheEthernet
subsystemandoptionalIOMmoduleslots.
•Group2(fans8and
9)islocatedinthebackleftoftheswitchbehindGroup1tocooltheCPU
subsystem.
•Group3(fans4,5,6,and7)islocatedoneithersideofthepowerslotstocoolthepower
supplies
FanspeedsaredeterminedbythermalsensorslocatedthroughouttheG3
system.Thefirmware
samplestheappropriatethermal sensorsatregularintervals,andsetstheappropriatefanspeeds.
Fangroup1drivesairflowacrossthefrontportionofthechassis,andfangroups2and3driveair
flowacrosstherearportionofthechassis.