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Junos OS runs on the following Juniper Networks® hardware: ACX Series, EX Series, M Series, MX Series, NFX Series, PTX Series, QFabric systems, QFX Series, SRX Series, T Series, JRR Series, and Junos Fusion.

These release notes accompany Junos OS Release 19.4R3 for the ACX Series, cRPD, EX Series, JRR Series, Junos Fusion, MX Series, NFX Series, PTX Series, QFX Series, SRX Series, vMX, vRR, and vSRX. They describe new and changed features, limitations, and known and resolved problems in the hardware and software.

  • Feature Guides Are Renamed As User Guides—Starting with Junos OS 19.4R1, we renamed our Feature Guides to User Guides to better reflect the purpose of the guides. For example, the BGP Feature Guide is now the BGP User Guide. We didn’t change the URLs of the guides, so any existing bookmarks you have will continue to work. To keep the terminology consistent on our documentation product pages, we renamed the Feature Guides section to User Guides. To find documentation for your specific product, check out this link.

  • New In Focus Guide—Starting on Junos Release 19.4, we are introducing a new document called In Focus that provides details on the most important features for the release in one place. We hope this document will quickly get you to the latest information about Junos features. Let us know if you find this information useful by sending email to

  • Important Information: