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    Perform a Swap Test on a Redundant MCS

    Purpose

    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 FPC and Switching and Forwarding Module (SFM). You can perform a swap test on the MCS to try to pinpoint the problem.

    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.

    Action

    To perform a swap test on the 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. Lay 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 with the following command:
      user@host> show chassis environment mcs

      Or you can check the MCS LEDs. If the MCS belongs to the master host module, switch mastership to the standby host module 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 CLI operational mode and issue the following command:
      user@host> request system halt

      The command shuts down the Routing Engine cleanly, so its state information is preserved.

      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.
    12. Verify correct MCS functioning by using the show chassis environment mcs command.

    If the replacement MCS works, you can be certain that the replaced MCS failed.

     

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    Published: 2012-08-20