M120 Component Redundancy - Juniper M120 Hardware Manual

M120 Multiservice Edge Router Hardware Guide
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M120 Component Redundancy

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4
with fast switchover times and higher bandwidth PFEs provide support for larger numbers
of PICs.
M120 Router Chassis Description on page 7
M120 Router Physical Specifications on page 82
M120 Router Environmental Specifications on page 86
M120 Router Power Requirements on page 88
A fully configured router is designed so that no single point of failure can cause the entire
system to fail. Only a fully configured router provides complete redundancy. All other
configurations provide partial redundancy. The following major hardware components
are redundant:
Host subsystem—The host subsystem requires a Routing Engine to be installed directly
into the CB. The router can have one or two host subsystems. If two host subsystems
are installed, one functions as the master and the other functions as the backup. If the
master host subsystem (or either of its components) fails, the backup can take over
as the master.
Power supplies—A router with two AC power supplies or two DC power supplies is fully
power redundant. In both AC and DC configurations, the power supplies share the load
almost evenly.
CAUTION: Mixing AC and DC power supplies is not supported. The first
power supply powered on will electrically disable the second power supply
without damaging any components in the system.
Cooling system—The cooling system has redundant components, which are controlled
by the host subsystem. If one of the fans fails, the host subsystem increases the speed
of the remaining fans to provide sufficient cooling for the router indefinitely.
M120 Router Chassis Description on page 7
M120 Host Subsystem Description on page 21
M120 AC Power Supply Description on page 72
M120 DC Power Supply Description on page 72
M120 Cooling System Description on page 19
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