[SRX] Devices inoperable and unable to bring FPCs online after upgrading version 18.2 or higher

Summary:

All SRX devices are inoperable after OS upgrade from version 15.1 to 18.2 and higher if physical fab link is enabled or disabled.

Symptoms:

Once the SRX is upgraded from 15.1 to 18.2 or higher, the device does not correctly load and is not able to bring FPCs online.

root> show chassis hardware 
error: Could not connect to node0 : No route to host

The following messages are also observed:

Dec 14 03:46:35   dcd[13334]: UI_CONFIGURATION_ERROR: Process: dcd, path: [edit interfaces], statement: fab0,  fabric member device enable/disable setting is not allowed

Cause:

There is a code change after 15.1 to check and prevent any enabled or disabled physical fab link to be committed. Even if a validation is enabled prior to upgrading to 18.2 or higher, the validation will succeed but the device will not correctly load after loading the new image.

set interfaces xe-2/2/0 enable
set interfaces xe-5/2/0 enable

set interfaces fab0 fabric-options member-interfaces xe-2/2/0
set interfaces fab1 fabric-options member-interfaces xe-5/2/0
request system software /var/log/junos-install-srx5000-x86-64-18.2R3-S2.9.tgz validate   Checking compatibility with configuration
Initializing...
Verified manifest signed by PackageProductionEc_2019 method ECDSA256+SHA256
Using /var/log/junos-install-srx5000-x86-64-18.2R3-S2.9.tgz
Hardware Database regeneration succeeded
Validating against /config/juniper.conf.gz
mgd: commit complete
Validation succeeded

According to the documentation on Upgrading and Downgrading to Junos with Upgraded FreeBSD, there are circumstances under which you cannot validate the running configuration in this way. One such circumstance is when you are upgrading to Junos OS with upgraded FreeBSD from Junos OS based on FreeBSD 6.1. This is the reason why the validation succeeded and does not detect the configuration conflict.

Solution:

Delete any enable or disable configuration from physical interfaces that are related to fab links prior to upgrading since there is no use case to enable or disable those links.

Knowledge Base