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Routing Engine

The Routing Engine is an Intel-based PC platform that runs JUNOS software. Software processes that run on the Routing Engine maintain the routing tables, manage the routing protocols used on the device, control the device interfaces, control some chassis components, and provide the interface for system management and user access to the device.

You can install only one Routing Engine in the device. The Routing Engine installs into the front of the chassis in the horizontal slot in the SCB labeled 0 or 1.

A USB port on the Routing Engine accepts a USB memory card that allows you to load JUNOS software.

Figure 12: Routing Engine

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Routing Engine Components

The Routing Engine (shown in Figure 12) consists of the following components:

Figure 13: USB Memory Device in a Routing Engine

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The Routing Engine has four LEDs that indicate its status. The LEDs, labeled MASTER, HDD, ONLINE, and FAIL, are located directly on the faceplate of the Routing Engine. Table 12 describes the functions of the Routing Engine LEDs.

Table 12: Routing Engine LEDs







On steadily

Routing Engine is Master.



Green blinking

Hard disk is functioning normally.




On steadily

Routing Engine is transitioning online.

Routing Engine is functioning normally.



On steadily

Routing Engine has failed.

Routing Engine Interface Ports and Status Indicators

In the center of the Routing Engine are three ports that connect the Routing Engine to one or more external devices on which system administrators can issue JUNOS command-line interface (CLI) commands to manage the device (see Figure 12).

The ports with the indicated labels function as follows:

For information about the pinouts for the connectors, see Cable Connector Pinouts.

Routing Engine Boot Sequence

The Routing Engine boots from the storage media in this order: the USB device (if present), then the internal flash disk, then the hard disk, then the LAN.

If the Routing Engines are configured for graceful switchover, the backup Routing Engine automatically synchronizes its configuration and state with the master Routing Engine. Any update to the master Routing Engine state is replicated on the backup Routing Engine. If the backup Routing Engine assumes mastership, packet forwarding continues through the services gateway without interruption. For more information about graceful switchover, see the JUNOS System Basics Configuration Guide.

Note: For specific information about Routing Engine components (for example, the amount of DRAM), issue the show chassis routing-engine command.

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