M120 Host Subsystem Description; M120 Routing Engine Overview; M120 Routing Engine Description - Juniper Networks Hardware Manual

M120 Multiservice Edge Router Hardware Guide

M120 Host Subsystem Description

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M120 Routing Engine Overview

M120 Routing Engine Description

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The host subsystem provides the routing and system management functions of the
router. You can install one or two host subsystems on the router. Each host subsystem
functions as a unit; the Routing Engine must be installed directly into the Control Board.
NOTE: We recommend you install two host subsystems for redundant
protection. If you install only one host subsystem, we recommend you install
it in slot CB0 .
Each host subsystem has three LEDs that display its status. The host subsystem LEDs
are located in the middle of the craft interface. For more information about the host
subsystem LEDs, see "Host Subsystem LEDs on the M120 Craft Interface" on page 26.
The host subsystem consists of the following components:
Taking the M120 Host Subsystem Offline on page 140
Maintaining the M120 Host Subsystem on page 104
M120 Routing Engine Description on page 18
M120 Control Board (CB) Description on page 21
M120 Routing Engine Description on page 18
M120 Routing Engine LEDs on page 21
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
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 140.
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. installs below
RE0
not power up if it is not installed into the CB.
, and installs below
CB0 RE1
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and . If two
CB0 CB1
. A Routing Engine does
CB1