Just a very quick few Juniper QFX related notes, probably more for personal future reference than an actual guide here, but may be useful to know!

Juniper QFX stuck in “Fabric with mixed devices” mode.

Typically a QFX comes from the factory in “Virtual Chassis with similar devices” mode when running “show virtual-chassis mode”. However, I discovered that one newly received QFX was showing in “Fabric with mixed devices” even after factory defaulting and even with a “request system zeroize”.

It’s a very simple fix but not particularly well documented and certainly a head scratcher and took longer than I’d like to admit to discover especially when expecting a factory reset to actually… reset to factory default.

request virtual-chassis mode fabric mixed disable reboot

JUNOS Host Software differs to actual Junos on the device.

You might find that the “JUNOS Host Software” differs to the actual Junos version on the device.
This is common in the Juniper QFX5100 and EX4600 for example where the Host OS is not automatically upgraded however not exclusive to those devices.
Although it is not necessary for Host and JunOS versions to match (unless otherwise specified in release notes), you may like to have them matching for uniformity.

To resolve this you simply need to add the “force-host” parameter to the end of your “request system software add” command. For example:

request system software add /mnt/jinstall-host-qfx-5-17.2R2.8-signed.tgz no-validate force-host

An excerpt from a Juniper KB here:

NOTE: On QFX5100 and EX4600 switches, the Host OS is not upgraded automatically, so you must use the force-host option if you want the Junos OS and Host OS versions to be the same.
However, pay attention to these notes regarding Junos OS and Host OS versions:

The Junos OS and Host OS versions do not need to be the same.
During an ISSU, the Host OS cannot be upgraded.
Upgrading the Host OS is not required for every software upgrade, as noted above.
If you are downgrading from Junos OS Release 14.1X53-D40 to any release earlier than 14.1X53-D40, you must use the force-host option or else the switch will issue core dumps.

More reading here.

For more Juniper related notes, see here.