Understanding Ex9214 Switch Component And Functionality Redundancy - Juniper EX9214 Hardware Manual

Understanding EX9214 Switch Component and Functionality
Redundancy
The Juniper Networks EX9214 Ethernet Switch is available as a fully redundant system. A redundant
EX9214 switch configuration is so designed that no single point of failure can cause the entire switch to
fail. See "EX9214 Switch Configurations" on page
The following hardware components provide redundancy to an EX9214 switch:
• Host subsystem—The host subsystem consists of a Routing Engine functioning together with a
Switch Fabric. The host subsystem performs switching and routing functionality, system
management, and system control functions of the switch. Either two or three host subsystems can be
installed in the switch. If two host subsystems are installed, one functions as the primary and the
other functions 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 Routing 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 Routing Engines are configured for graceful switchover, the backup Routing Engine
automatically synchronizes its configuration and state with the primary Routing Engine. Any update
to the primary Routing Engine state is replicated on the backup Routing Engine. If the backup
Routing Engine assumes primary role, packet forwarding continues through the switch without
interruption.
• AC power supplies—You can install either two or four AC power supplies vertically at the rear of the
chassis in slots PEM0 through PEM3 (left 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
configuration is removed or fails, its redundant power supply takes over without interruption. 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
• DC power supplies—You can install four DC power supplies vertically at the rear of the chassis in
slots PEM0 through PEM3 (left 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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