Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


Known Limitations

Learn about known limitations in Junos OS Release 21.4R1 for EX Series switches.

For the most complete and latest information about known Junos OS defects, use the Juniper Networks online Junos Problem Report Search application.

General Routing

  • When the device is up and running for a long time, there is a possibility FS gets bad blocks and it is accumulated. When any change done to it, it reloads and tries to recover the bad blocks from the FS. PR910445

  • BUM (Broadcast, Unknown Unicast, and Multicast) traffic replication over VTEP is sending out more packets than expected and there seems to be a loop also in the topology.PR1570689


  • Junos OS Release 21.1 and lower are running on FreeBSD version 11 whereas from Junos OS Release 21.2 onward, the FreeBSD version is 12. Software upgrade to Junos OS Release 21.2 or later from Junos OS Release 21.1 or earlier will mandatorily need CLI configuration statement no-validate to be used during software image upgrade process. (For EX4400 platforms, this is applicable from version 21.3 onward. Hence, for EX4400 platforms, software upgrade to 21.3 (or later) from 21.2 (or earlier) will mandatorily need CLI configuration statement no-validate during software image upgrade process.) PR1586481

High Availability

  • Starting in Junos OS Release 21.4R1, EX4650 switches support unified in-service software upgrade (ISSU). However, EX4650 switches provide unified ISSU support only if the Cancun versions in the chipset SDK are the same in the current version and the version you are upgrading to. PR1634695