• Supported Platforms
• M120 Routers

• Related Topics
• M120 Routing Engine Description
• Routing Engine Interface Ports and Status Indicators on the M120 Craft Interface

Replacing an M120 Routing Engine

Removing an M120 Routing Engine

The router can have one or two Routing Engines. They are located within the CB in the rear of the chassis on either side of the FEBs in the slots marked CB0 and CB1. Each Routing Engine weighs approximately 2.4 lb (1.1 kg).

Caution: Before you replace a Routing Engine, you must take the host subsystem offline. If there is only one host subsystem, taking the host subsystem offline shuts down the router. See Taking the M120 Host Subsystem Offline.

Caution: If the Routing Engine to be replaced is currently functioning as the master Routing engine, switch it to be the backup before removing it. See Taking the M120 Host Subsystem Offline.

To remove a Routing Engine from a CB (see Figure 1):

1. Take the host subsystem offline as described in Taking the M120 Host Subsystem Offline.
2. Place an electrostatic bag or antistatic mat on a flat, stable surface.
3. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
4. Press the red tabs on the ejector handles on both sides of the Routing Engine faceplate.
5. Flip the ejector handles outward to unseat the Routing Engine.
6. Grasp the Routing Engine by the ejector handles and slide it about halfway out of the chassis.
7. Place one hand underneath the Routing Engine to support it and slide it completely out of the chassis.
8. Place the Routing Engine on the antistatic mat.

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

Installing an M120 Routing Engine

To install a Routing Engine into a CB (see Figure 2):

1. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
2. Ensure that the ejector handles are not in the locked position. If necessary, press the red tabs and flip the ejector handles outward.
3. Place one hand underneath the Routing Engine to support it. With the other hand, grasp one of the ejector handles on the faceplate.
4. Carefully align the sides of the Routing Engine with the guides inside the opening on the CB.
5. Slide the Routing Engine into the CB until you feel resistance, then press the Routing Engine's faceplate until it engages the connectors.
6. Press both the ejector handles inward to seat the Routing Engine.

   The Routing Engine might require several minutes to boot.

7. 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 OK LED lights steadily. If the red FAIL LED lights steadily instead, remove and install the Routing Engine again (see Removing an M120 Routing Engine and Installing an M120 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 OS documentation.