Juniper M120 - M120 Routing Engine Description

• M120 Control Board (CB) Description on page 47
M120 Routing Engine Description
The Routing Engine runs the Junos OS. The software processes that run on the Routing
Engine maintain the routing tables, manage the routing protocols used on the router,
control the router interfaces, control some chassis components, and provide the interface
for system management and user access to the router.
You can install one or two Routing Engines in the router. The Routing Engines install into
the rear of the chassis in vertical slots directly into the CB labeled CB0 and CB1. If two
Routing Engines are installed, one functions as the master and the other acts as the
backup. If the master Routing Engine fails or is removed, and the backup is configured
appropriately, the backup takes over as the master. For detailed information, see “Taking
the M120 Host Subsystem Offline” on page 267.
If the host system is redundant, the backup Routing Engine is hot-removable and
hot-insertable, but the master Routing Engine is hot-pluggable. A Routing Engine that is
not redundant is hot-pluggable. Each Routing Engine requires a CB to be installed in the
adjacent slot. RE0 installs below CB0, and RE1 installs below CB1. A Routing Engine does
not power up if it is not installed into the CB.
NOTE: If two Routing Engines are installed, they must both be the same
hardware model.
There is a USB memory device that connects directly into the front of Routing Engine.
The USB port allows you to plug in a USB keychain device.
Figure 10: M120 Routing Engine
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M120 Multiservice Edge Router Hardware Guide