Understanding EX9214 Switch Component and Funconality
Redundancy
The Juniper Networks EX9214 Ethernet Switch is available as a fully redundant system. A redundant
EX9214 switch conguraon is so designed that no single point of failure can cause the enre switch to
fail. See "EX9214 Switch Conguraons" on page 9.
The following hardware components provide redundancy to an EX9214 switch:
• Host subsystem—The host subsystem consists of a Roung Engine funconing together with a
Switch Fabric. The host subsystem performs switching and roung funconality, system
management, and system control funcons of the switch. Either two or three host subsystems can be
installed in the switch. If two host subsystems are installed, one funcons as the primary and the
other funcons as the backup. If the primary host subsystem (or either of its components) fails, the
backup takes over as the primary. To operate, each host subsystem requires a Roung Engine module
(RE module) installed directly into in a Switch Fabric module (SF module).
You can install up to 12 line cards in an EX9214 switch. You can install either a line card or an SF
module in the slot nine (labeled 2 | 6). If you install a line card in slot nine (labeled 2 | 6), redundancy
is not available for the host subsystem.
If the Roung Engines are congured for graceful switchover, the backup Roung Engine
automacally synchronizes its conguraon and state with the primary Roung Engine. Any update
to the primary Roung Engine state is replicated on the backup Roung Engine. If the backup
Roung Engine assumes primary role, packet forwarding connues through the switch without
interrupon.
• AC power supplies—You can install either two or four AC power supplies vercally at the rear of the
chassis in slots PEM0 through PEM3 (leî™› to right). The power supplies operate in two zones: power
supplies in slots PEM0 and PEM2 provide power to the lower fan tray, line-card slots 6 through 11,
and switch fabric slots 1 and 2; power supplies in slots PEM1 and PEM3 provide power to the upper
fan tray, line-card slots 0 through 5, and switch fabric slot 0. There must be at least one power supply
in each zone. Four power supplies provide full redundancy. If a power supply in a redundant
conguraon is removed or fails, its redundant power supply takes over without interrupon. The
power supply in PEM2 serves as redundant power supply to the power supply in slot PEM0 and the
power supply in PEM3 serves as redundant power supply to the power supply in slot PEM1. If only
two power supplies are installed, they must be installed in slots PEM0 and PEM1 or in slots PEM2
and PEM3. See "AC Power Supply in an EX9214 Switch" on page 43.
• DC power supplies—You can install four DC power supplies vercally at the rear of the chassis in
slots PEM0 through PEM3 (leî™› to right). The power supplies operate in two zones: power supplies in
slots PEM0 and PEM2 provide power to the lower fan tray, line-card slots 6 through 11, and switch
fabric slots 1 and 2; power supplies in slots PEM1 and PEM3 provide power to the upper fan tray,
line-card slots 0 through 5, and switch fabric slot 0. There must be at least one power supply in each
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