Juniper Networks EX8208 manual Routing Engine and Control Redundancy, Switch Fabric Redundancy

Complete Hardware Guide for EX8208 Ethernet Switches

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
Switch Configuration	Slot SRE0	Slot SRE1	Slot SF	Control Redundancy
Base configuration	SRE module	Empty	SF module	No
Base configuration	Empty	SRE module	SF module	No
User-defined	SRE module	SRE module	Empty	Yes
configuration
Redundant	SRE module	SRE module	SF module	Yes
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
Switch Configuration	Slot SRE0	Slot SRE1	Slot SF	Redundancy
Base configuration	SRE module	Empty	SF module	No

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