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
681Copyright © 2012, Juniper Networks, Inc.
Chapter 35: Monitoring Redundant MCSs
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