This article addresses the likely cause of a chassis-control error that can occur when performing a unified in-service software upgrade (ISSU) on an MX104 router.

When performing a unified ISSU on an MX104 router, the upgrade fails with the following error:

error: Unrecognized command (chassis-control)
warning: The FPC state on LCC may not be ONLINE

The likely cause of this error is that the unified ISSU is run on a version of the Junos OS below 14.1R1, whereas the unified ISSU is not available on the MX104 until Junos OS 14.1R1.

Run a unified ISSU only on Junos OS 14.1R1 and above.

To upgrade an MX104 router to a version of the Junos OS below 14.1R1, use a standard upgrade instead of a unified ISSU.

If you encounter this chassis-control error when performing a unified ISSU on an MX104 router running Junos OS 14.1R1 and above, please Open a Case with JTAC .