Routing Engines for the M120 Router

The Routing Engine is an Intel-based Peripheral Component Interconnect (PCI) 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 rear of the chassis in vertical slots directly into the Control Board (CB) labeled CB0 and CB1. 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.

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. RE0 installs below CB0, and RE1 installs below CB1. A Routing Engine does not power up if it is not installed into the CB.

There is a USB memory device that connects directly into the front of the Routing Engine. The USB port allows you to plug in a USB keychain device.

Figure 12: Routing Engine

Routing Engine Components

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

• CPU—Runs JUNOS software to maintain the router's routing tables and routing protocols. It has a Pentium-class processor.
• DRAM—Provides storage for the routing and forwarding tables and for other Routing Engine processes.
• USB port—Provides a removable media interface through which you can install the JUNOS software manually. See Figure 13. JUNOS supports USB version 1.0.
• Internal flash disk—Provides primary storage for software images, configuration files, and microcode. The disk is a fixed compact flash and is inaccessible from outside the router.
• Hard disk—Provides secondary storage for log files, memory dumps, and rebooting the system if the internal compact flash disk fails.
• LED—Indicates disk activity for the internal IDE interface. It does not necessarily indicate routing-related activity.
• HDD LED—Indicates disk activity for the hard disk drive.
• Interfaces for out-of-band management access—Provide information about Routing Engine status to devices (console, laptop, or terminal server) that can be attached to access ports located on the Routing Engine.

  Each Routing Engine has one 10/100-Mbps Ethernet port for connecting to a management network, and two asynchronous serial ports—one for connecting to a console and one for connecting to a modem or other auxiliary device.

• EEPROM—Stores the serial number of the Routing Engine.
• Reset button—Reboots the Routing Engine when pressed.
• Offline button—Takes the Routing Engine offline when pressed.
• Extractor clips—Control the locking system that secures the Routing Engine.

Figure 13: USB Memory Device in a Routing Engine

Each Routing Engine has two LEDs that indicates its status. The LEDs, labeled ONLINE and HDD, are located directly on the faceplate of the Routing Engine. Table 5 describes the functions of the Routing Engine LEDs.

Table 5: Routing Engine LEDs

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.

Note: The LEDs that report host module status (including Routing Engine status) are on the craft interface rather than the Routing Engine faceplate.

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 M120 Router

Removing a 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 Forwarding Engine Boards (FEBs) in the slots marked CB0 and CB1. Each Routing Engine weighs approximately 2.4 lb (1.1 kg).

To remove a Routing Engine from a CB (see Figure 14):

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. 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, install a replacement Routing Engine as soon as possible.

Figure 14: Removing a Routing Engine

Installing a Routing Engine

To install a Routing Engine into a CB (see Figure 15):

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. Verify that the router is attached to a proper earth ground.
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 chassis.
5. Slide the Routing Engine into the chassis until you feel resistance, and then press the Routing Engine's faceplate until it engages the midplane connectors.
6. Press both the ejector handles inward to seat the Routing Engine.

   The Routing Engine might require several minutes to boot.

7. If applicable, tighten the screws on the extractor handles, using a Phillips screwdriver. Be sure to tighten the screws enough to seat the Routing Engine properly.
8. 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 Replacing a Routing Engine in an M120 Router 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 15: Installing a Routing Engine