Routing Engine And Control Redundancy - Juniper EX8208 Hardware Manual

When the SRE modules are configured for graceful switchover, the backup SRE module automatically
synchronizes its configuration and state with those of the primary SRE module. Any update to the primary
SRE module is replicated on the backup SRE module. If the backup module assumes primary role, packet
forwarding continues through the switch.
Power supplies—You can install up to six AC or six DC power supplies in an EX8208 switch. Each power
supply connects to the backplane of the chassis, which distributes the output power produced by the
power supplies to different switch components. (See
Each power supply provides power to all the components in the switch.
An N+1 power configuration is required for Juniper Networks EX8200 Ethernet Switches. In an N+1
power configuration, if one power supply fails or is removed, the remaining power supplies continue to
supply power for the entire system without interruption. If dual power feed redundancy is required, the
required power configuration is N+N. The DC power supplies provide independent A and B power feeds
so that dual power redundancy is available even in an N+1 power configuration. See
in an EX8200 Switch" on page 56
Cooling system—The cooling system in an EX8200 switch consists of a single fan tray. The fan tray
contains 12 fans. Under normal operating conditions, the fans in the fan tray run at less than full speed.
The fans are controlled by two fan tray controllers. The fans are numbered 1 through 12. Fans 1 through
6 are controlled by the first fan tray controller. Fans 7 through 12 are controlled by the second fan tray
controller. If one fan tray controller fails, the other 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
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 primary 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 9 on page 39 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.
"Backplane in an EX8208 Switch" on page
and "DC Power Supply in an EX8200 Switch" on page
"AC Power Supply
70.
"EX8208 Cooling System" on
38
49.)