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Routing Engines for the MX240, MX480, and MX960 Ethernet Services Routers

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 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 front of the chassis in slots directly into the Switch Control Boards (SCBs) labeled 0 and 1. 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.

On the MX960 router, a Routing Engine installed in SCB slot 2/6 receives no power and supplies no additional routing functions. If no SCB is installed in slot 2/6, install a blank panel in the slot.

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 must be installed directly into an SCB. A USB port on the Routing Engine accepts a USB memory device that allows you to load JUNOS software.

Figure 20: Routing Engine 1300

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Routing Engine Components

Each Routing Engine (shown in Figure 20) consists of the following components:

Figure 21: USB Memory Device in a Routing Engine of an MX240 Router

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Figure 22: USB Memory Device in a Routing Engine of an MX480 Router

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Figure 23: USB Memory Device in a Routing Engine of an MX960 Router

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Each Routing Engine has four LEDs that indicates its status. The LEDs, labeled MASTER, HDD, ONLINE, and FAIL are located directly on the faceplate of the Routing Engine. Table 6 describes the functions of the Routing Engine LEDs.

Table 6: 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 Boot Sequence

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

Note: If two Routing Engines are installed, they must both be the same hardware version.

Replacing a Routing Engine in an MX240, MX480, or MX960 Ethernet Services Router

The Routing Engine is hot-pluggable. If the router contains a redundant host subsystem, the Routing Engine and control board are hot-removable and hot-insertable. Before you replace a control board or a Routing Engine, you must take the host subsystem offline (see the hardware guide for your routing platform).

Removing a Routing Engine

The router can have one or two Routing Engines. They are located within the SCB in the front center of the chassis in the slots marked 0, and 1. On the MX960 router, a spare Routing Engine can be installed in slot 2/6, but it will not receive power. Each Routing Engine weighs approximately 2.4 lb (1.1 kg).

To remove a Routing Engine from an SCB (see Figure 24, Figure 25, and Figure 26):

  1. Place an electrostatic bag or antistatic mat on a flat, stable surface.
  2. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist and connect the strap to one of the ESD points on the chassis. Make sure the router is attached to a proper earth ground.
  3. Check whether the Routing Engine is functioning as the backup or as the master. If necessary, take the host subsystem offline as described in the hardware guide for your routing platform.

    Note: Router performance might change if the standby Routing Engine's configuration differs from the former master's configuration. For the most predictable performance, configure the two Routing Engines identically, except for parameters unique to a Routing Engine, such as the hostname defined at the [edit system] hierarchy level and the management interface (fxp0 or equivalent) defined at the [edit interfaces] hierarchy level.

    To configure Routing Engine-specific parameters and still use the same configuration on both Routing Engines, include the appropriate configuration statements under the re0 and re1 statements at the [edit groups] hierarchy level and use the apply-groups statement. For instructions, see the JUNOS System Basics Configuration Guide.

  4. Verify that the Routing Engine LEDs are off.
  5. Loosen the captive screws at each end of the Routing Engine.
  6. Flip the ejector handles outward to unseat the Routing Engine.
  7. Grasp the Routing Engine by the ejector handles and slide it about halfway out of the chassis.
  8. Place one hand underneath the Routing Engine to support it and slide it completely out of the chassis.
  9. Place the Routing Engine on the antistatic mat.

    Note: To maintain proper airflow through the chassis, do not leave an SCB installed in the chassis without a Routing Engine for extended periods of time. If a Routing Engine is removed, install a replacement Routing Engine as soon as possible.

Figure 24: Removing a Routing Engine from an MX240 Router

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Figure 25: Removing a Routing Engine from an MX480 Router

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Figure 26: Removing a Routing Engine from an MX960 Router

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Installing a Routing Engine

To install a Routing Engine into an SCB (see Figure 27, Figure 28, and Figure 29):

  1. Ensure that the ejector handles are not in the locked position. If necessary, flip the ejector handles outward.
  2. Place one hand underneath the Routing Engine to support it.
  3. Carefully align the sides of the Routing Engine with the guides inside the opening on the SCB.
  4. Slide the Routing Engine into the SCB until you feel resistance, and then press the Routing Engine's faceplate until it engages the connectors.
  5. Press both the ejector handles inward to seat the Routing Engine.
  6. Tighten the captive screws at each end of the Routing Engine.

The Routing Engine might require several minutes to boot.

After the Routing Engine boots, verify that it is installed correctly by checking the RE0 and RE1 LEDs on the craft interface. If the router is operational and the Routing Engine is functioning properly, the green ONLINE LED lights steadily. If the red FAIL LED lights steadily instead, remove and install the Routing Engine again (see Removing a Routing Engine and Installing a Routing Engine). If the red FAIL LED still lights steadily, the Routing Engine is not functioning properly. Contact your customer support representative.

To check the status of the Routing Engine, use the CLI command:

user@host> show chassis routing-engine

Routing Engine status:   
  Slot 0:
    Current state                 Master

For more information about using the CLI, see the JUNOS software manuals.

Figure 27: Installing a Routing Engine in an MX240 Router

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Figure 28: Installing a Routing Engine in an MX480 Router

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Figure 29: Installing a Routing Engine in an MX960 Router

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