Ptx5000 Field-Replaceable Units - Juniper PTX5000 Hardware Manual

• Centralized Clock Generators (CCGs)—The PTX5000 has a standard configuration of one CCG. If two
CCGs are installed, the second CCG functions as backup. If one CCG fails, the other becomes the
primary CCG. Primary Role of the CCG is independent of the host subsystem, so routing functions
are not affected. See
• Power system—The PTX5000 has two redundant, load-sharing power distribution units (PDUs),
located at the lower rear of the chassis in slots PDU0 on the right and PDU1 on the left. The PDUs
are hot-removable and hot-insertable. When the PTX5000 is operating normally and both PDUs are
switched on, load sharing between them occurs automatically. If one PDU fails in a fully redundant
power system, the other PDU can provide full power to the PTX5000 indefinitely.
NOTE: Redundant PDUs must be the same model number during normal operations.
The PDUs provide connections for the DC power cables or AC power cords; configure the output
voltages produced by the power supply modules (PSMs); and connect to the midplane, which
distributes the different output voltages to PTX5000 components, depending on their voltage
requirements. The number of PSMs required for full redundancy varies depending on the
configuration of the chassis.
NOTE: The normal-capacity power system distributes power into three different output
zones. The high-capacity power system does not use power zones. See the
Normal-Capacity Power System Power Zones" on page 182
normal-capacity power system power zones.
• 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 PTX5000 indefinitely. See

PTX5000 Field-Replaceable Units

Field-replaceable units (FRUs) are router components that can be replaced at the customer site.
Replacing most FRUs requires minimal router downtime. The PTX5000 uses the following types of
FRUs:
• Hot-removable and hot-insertable FRUs—You can remove and replace these components without
powering off the PTX5000 or disrupting the routing functions.
• Hot-pluggable FRUs—You can remove and replace these components without powering down the
PTX5000, but the routing functions of the system are interrupted when the component is removed.
"PTX5000 Centralized Clock Generator Description" on page 29.
"Understanding
for more information about
"PTX5000 Cooling System" on page
12
32.