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Understanding the Host Subsystem

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Host Subsystem Overview on page 368

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M120, M320 T320, T640, T1600, TX Matrix, and TX Matrix Router Routing

Engines on page 369

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M120, M320, T320, T640, T1600, TX Matrix, and TX Matrix Plus Router Control

Boards on page 371

Host Subsystem Overview

To replace the cable management system, see the appropriate router hardware guide.

Inspect the host subsystem to ensure that the Routing Engine and Control Board function

properly.

The host subsystem provides routing and system management functions on the M120,

M320, T320, T640, and T1600 routers. The host subsystem is comprised of two

components: the Routing Engine and the Control Board. For a host subsystem to function,

both of these components must be installed and operational.

The Routing Engine maintains the routing tables used by the router and controls the

routing protocols that run on the router.

The Control Board provides control and monitoring functions for the router—determining

Routing Engine mastership, controlling power, performing reset and SONET clocking for

the other router components, monitoring and controlling fan speed, and monitoring

system status using I2C controllers.

You can install one or two host subsystems on the router. You can install one or two

Routing Engines. The Routing Engines install into the upper rear of the chassis in the slots

labeled RE0 and RE1. If two Routing Engines are installed, one functions as master and

the other acts as backup. If the master Routing Engine fails or is removed, and the backup

is configured appropriately, the backup restarts and becomes master. The Routing Engines

are hot-pluggable. Each Routing Engine requires that a Control Board be installed in the

adjacent slot.

The Control Boards install into the upper rear of the chassis in the slots labeled CB0 and

CB1. If two Control Boards are installed, one functions as master and the other acts as

backup. If the master Control Board fails or is removed, the backup restarts and becomes

master. The Control Boards are hot-pluggable. Each Control Board requires a Routing

Engine to be installed in the adjacent slot. CB0 installs above RE0, and CB1 installs below

RE1. A Control Board does not function if no Routing Engine is present in the adjacent

slot.

Documentation

Checklist for Monitoring the Host Subsystem on page 367•

M Series and T Series Routers Monitoring and Troubleshooting Guide

Juniper M Series User Manual

Questions and Answers: