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    Verifying MCS Failure

    To verify MCS operation failure:

    1. Check the MCS Fuses
    2. Perform an MCS Swap Test

    Check the MCS Fuses


    To check for blown MCS fuses.


    The M40e and M160 router fuses are located in a fuse box at the rear of the midplane, behind the lower rear impeller assembly. You must remove the lower impeller assembly to access the fuses, as described in the appropriate router hardware guide.

    When the fuse for an MCS blows, the MCS stops functioning even though it is installed correctly and the power supplies are providing power to the router.

    For the M40e and M160 routers, when a fuse has blown but the power supplies are still delivering power to router, the amber LED adjacent to the fuse lights. See Figure 1.

    Figure 1: M40e M160 Router Fuses

    M40e M160 Router Fuses

    Another indication that a fuse has blown is that the colored indicator bulb inside it becomes visible through the clear cover on the fuse. For information about the indicator bulb color for each fuse type, see the appropriate router hardware guide.

    A blown fuse can cause a component to fail even though it is correctly installed and the power supplies are functioning. Check for a blown fuse in the following circumstances:

    • The LED that indicates normal operation for the component fails to light.
    • The appropriate show chassis environment command indicates that the component is installed but is not receiving power.

    Perform an MCS Swap Test


    The MCS can fail and not start, or it can cause a connectivity problem between the Routing Engine and the Packet Forwarding Engine components, such as the Flexible PIC Concentrator (FPC) and Switching and Forwarding Module (SFM). You can perform a swap test on the MCS to try to pinpoint the problem.

    Caution: The MCS is hot-pluggable. Routing functions are interrupted until a replacement is installed. You should perform a swap test during a maintenance window.

    Caution: Before performing a swap test, always check for bent pins in the midplane and check the MCS for stuck pins in the connector. Pins stuck in the component connector can damage other good slots during a swap test.


    To perform a swap test on an MCS, remove it and replace it with one that you know works.

    Normally, if two host modules are installed in the router, HOST0 functions as the master and HOST1 as the backup. You can remove the backup host module (or either of its components) without interrupting the functioning of the router. If you take the master host module offline, the router reboots and the backup host module becomes the master. If the router has only one host module, taking it offline causes the router to shut down.

    The host module is taken offline and brought back online as a unit. Before you replace the Routing Engine or an MCS, you must take the host module offline; the host module is hot-pluggable.

    To remove an MCS:

    1. Place an electrostatic bag or antistatic mat on a flat, stable surface to receive the Routing Engine.
    2. Attach an electrostatic discharge (ESD) strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
    3. Remove the rear component cover by loosening the screws at the corners of the cover and pulling it straight off of the chassis.
    4. If two host modules are installed, check whether the MCS you are removing belongs to the master host module. Use the show chassis environment mcs command or check the MCS LEDs. If it does, switch mastership to the standby host module. You can change the default mastership by including the routing-engine statement at the [edit chassis redundancy] hierarchy level in the configuration, as described in the Junos OS System Basics Configuration Guide.
    5. On the console or other management device connected to the Routing Engine that is paired with the MCS you are removing, enter the operational mode and issue the following command. The command shuts down the Routing Engine cleanly, so its state information is preserved.
      user@host> request system halt

      Wait to continue until all software processes have shut down.

    6. Flip the ends of the extractor clips outward.
    7. Grasp the extractor clips and slide the unit about halfway out of the chassis.
    8. Place one hand under the MCS to support it, slide it completely out of the chassis, and place it on the antistatic mat or in the electrostatic bag.
    9. Align the rear of the MCS with the guides inside the chassis and slide it in completely.
    10. Press the extractor clips on the left and right sides of the MCS inward.
    11. Verify that the green LED labeled OK on the MCS faceplate is lit. Also check the host module LEDs on the craft interface to verify that the green LED labeled ONLINE is lit for the host module to which the MCS belongs.

      You can also verify correct MCS functioning by using the show chassis environment mcs command.

    12. Reinstall the rear component cover and tighten the screws at the corners to secure it to the chassis.

    Related Documentation


    Published: 2012-08-20