Juniper Networks EX8208 - Manual (Page 38)

fan tray controller keeps half the fans working. This allows the switch to continue to
operate normally as long as the remaining fans cool the chassis sufficiently.
The fan tray continues to operate indefinitely and provides sufficient cooling even when
a single fan fails provided the room temperature is within the operating range. See
“Cooling System and Airflow in an EX8208 Switch” on page 53.
Routing Engine and Control Redundancy
Each SRE module contains switch fabric circuitry, Routing Engine circuitry, and switch
control and management circuitry. An EX8208 switch can have one SRE module or two
SRE modules. If a switch has two SRE modules, one functions as the master while the
other functions as a backup and is in standby mode. This provides the switch with full
redundancy (1+1) for Routing Engine and switch control functionality.
Table 3 on page 12 shows the available slots in the EX8208 chassis and the Routing
Engine and control redundancy associated with different SRE module and Switch Fabric
(SF) module combinations.
Table 3: Routing Engine and Control Redundancy for EX8208 Switches
Routing Engine and
Control Redundancy
Slot SF Slot SRE1 Slot SRE0 Switch Configuration
No SF module Empty SRE module Base configuration
No SF module SRE module Empty Base configuration
Yes Empty SRE module SRE module User-defined
configuration
Yes SF module SRE module SRE module Redundant
configuration
Switch Fabric Redundancy
The switch fabric circuitry in an EX8208 switch is distributed across three modules—two
SRE modules and one SF module. Any two of these three modules must be installed and
functional to provide a working switch fabric with no redundancy. The third module, when
present, provides partial redundancy (2+1) for the switching functionality, such that if
any one of the two functional modules becomes nonoperational, the third module takes
over.
Table 4 on page 12 shows the available slots in an EX8208 chassis and the switch fabric
redundancy associated with different SRE module and SF module combinations.
Table 4: Switch Fabric Redundancy for EX8208 Switches
Switch Fabric
Redundancy
Slot SF Slot SRE1 Slot SRE0 Switch Configuration
No SF module Empty SRE module Base configuration
Copyright © 2010, Juniper Networks, Inc. 12
Complete Hardware Guide for EX8208 Ethernet Switches