For MX10K-LC4800 - The ISSU support for Layer 2 and Layer 3 PFE features is targeted from 25.4R1 release
FPC will be rebooted if ISSU is attempted on non-supported version
root@MX10004-RE1> request vmhost software in-service-upgrade /var/tmp/junos-vmhost-install-mx-x86-64-24.2R1-S2.5.tgz reboot
Chassis ISSU no-enhanced-mode
[Jan 27 15:05:38]:ISSU: set chassis no-enhanced-mode
Chassis ISSU Check Done
[Jan 27 15:05:38]: Starting VMHOST ISSU
[Jan 27 15:05:38]:ISSU: Validating Image
[edit protocols router-advertisement]:
NSR is not supported; packet loss is expected
FPC 0 will be offlined (In-Service-Upgrade not supported)
FPC 1 will be offlined (In-Service-Upgrade not supported)
Do you want to continue with these actions being taken ? [yes,no]
Relevant Documentation:
Hardware details on LC4800:
https://www.juniper.net/documentation/us/en/hardware/mx-module-reference/mx10008/topics/concept/jnp10k-lc4800-line-card-descripion.html
List of Hardware that support ISSU
https://apps.juniper.net/feature-explorer/feature/2392?fn=Unified%20in-service%20software%20upgrade%20(Unified%20ISSU)