This KB describes about different scenarios while doing a firmware version on MX devices.
While doing firmware upgrade, users may encounter specific challenges or seek a more profound understanding of the upgrade process.
Q.1) What is the process to upgrade Junos for VMhost RE from 18.1R2 to 20.4 by bootable USB? Can Junos version can be upgraded directly to 20.4 ?
--> No, Junos version cannot be directly upgraded to 20.4 from 18.1R2.
Reason: Junos version: 19.3R1 or later supports firmware version: 6.x. Because of this reason, first firmware versions needs to be upgraded to version: 6.x and later Junos version upgrade can be done.
Steps:1) Verify if current Junos version supports i40e NVM firmware upgrade.For an example:Current Junos version on the device is 18.1R2 and it doesn't supports i40e NVM firmware upgrade, as verified from the table mentioned in link: TSB17603 [juniper.net]. Please refer below table for reference.
Platform
15.x
16.x
17.x
18.x
19.x
PTX5000
15.1F6-S11
16.1R7
17.1R3 / 17.2R3 / 17.3R3 / 17.4R2
18.1R1 / 18.2R3 / 18.3R1 / 18.4R1
19.1R1 or later
PTX3000
N/A
18.2R3 / 18.3R3 / 18.4R2
19.1R2 / 19.2R1
MX240/480/960
18.1R1 / 18.2R1 / 18.3R1 / 18.4R1
MX2010/2020
MX2008
MX10016/10008PTX10016/10008
Does current Junos version supports i40e NVM firmware upgrade ?
Yes, move to Step 3.
No, move to Step 2.
2) Upgrade current Junos version to a version which supports i40e NVM firmware upgrade as mentioned in Table 1.For example: Junos version: 18.1R2 doesn't supports i40e NVM firmware upgrade. Upgrading RE to supported Junos version: 18.4R1.3) Upgrade firmware version:Once RE is upgraded to a version which supports i40e NVM firmware upgrade, upgrade the firmware version by referring TSB17603 [juniper.net] .
Q.2) Can a VMhost RE upgraded directly from 18.4 to 21.4 by using bootable USB ? Current firmware version is 4.26, does firmware version also be upgraded or need to upgrade it separately ?--> Yes, firmware version will be directly upgraded to 7.0 along with Junos version.Reason: Junos OS Release 21.4 R1 or later VM Host image based on Linux WR LTS19. VM Host image based on Linux WR LTS19 have firmware version: 7.0 inbuilt. So, if the Junos OS version is upgraded to 21.4R1 or later using the standard Junos OS upgrade process, the i40e NVM firmware upgrade is done automatically during the upgrade process.However, it is important to note that, while doing Junos step upgrade installation i40e NVM version 6.01 is the prerequisite to install a LTS19 based image, else image installation will fail.
Please refer below link for more details: https://www.juniper.net/documentation/us/en/software/junos/junos-install-upgrade/topics/task/vmhost-nvm-upgrade.html