fantray controller keeps halfthe fans working. This allows the switch to continue to
operatenormally as long asthe remaining fans cool the chassis sufficiently.
Thefan traycontinues to operate indefinitelyand provides sufficient cooling even when
asingle fan fails provided the room temperatureis within the operating range. See
“CoolingSystem and Airflow in an EX8208 Switch”on page 53.
RoutingEngine and Control Redundancy
EachSRE module contains switch fabric circuitry,Routing Engine circuitry, and switch
controland management circuitry. An EX8208 switchcan have one SRE module or two
SREmodules. If a switch has two SRE modules, one functions asthe master while the
otherfunctions as a backup and is in standby mode. This provides the switchwith full
redundancy(1+1) for Routing Engine and switch controlfunctionality.
Table3 on page12 shows the available slots in the EX8208 chassis and the Routing
Engineand control redundancy associatedwith different SRE module and Switch Fabric
(SF)module combinations.
Table3: Routing Engine and Control Redundancyfor EX8208 Switches
RoutingEngine and
ControlRedundancySlotSFSlotSRE1SlotSRE0SwitchConfiguration
NoSFmoduleEmptySREmoduleBaseconfiguration
NoSFmoduleSRE moduleEmptyBaseconfiguration
YesEmptySREmoduleSREmoduleUser-defined
configuration
YesSFmoduleSRE moduleSREmoduleRedundant
configuration
SwitchFabric Redundancy
Theswitch fabric circuitry in an EX8208 switchis distributed across three modules—two
SREmodules and one SF module. Any twoof these three modules must be installed and
functionalto providea working switch fabric with no redundancy.The third module, when
present,provides partial redundancy (2+1) for the switchingfunctionality, such that if
anyone of the two functional modules becomes nonoperational,the third module takes
over.
Table4 on page12 shows the available slots in an EX8208 chassis and the switchfabric
redundancyassociated with different SRE moduleand SF module combinations.
Table4: Switch FabricRedundancy for EX8208 Switches
SwitchFabric
RedundancySlotSFSlotSRE1SlotSRE0SwitchConfiguration
NoSFmoduleEmptySREmoduleBaseconfiguration
Copyright© 2010, Juniper Networks,Inc.12
CompleteHardwareGuide for EX8208 Ethernet Switches