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Picking the right Junos version is important. If you’re not familiar with Juniper, finding and downloading the right software package is confusing. Here’s some guidance on picking the right version.
TLDR: Check the Suggested Releases page, find the latest service release in the suggested version for your platform. Almost never use the very latest version. Never use the version the box shipped with. Pay attention on the Downloads page, there are traps.
It’s useful to understand Junos version numbering, and the upgrade policy. Then check the Suggested Releases page to see what they recommend, check if that makes sense, and figure out how to get from here to there.
Understanding Version Numbering
These days Juniper publishes a new release train every quarter. Versioning is simple “<year>.<quarter>.R<release number>”. So 21.4R1 is released in the 4th quarter of 2021. New releases add new features and support new hardware. Configs may break
They then publish “service releases” on top of that, for example 21.4R1-S1 and 21.4R1-S2. These are supposed to only be bugfixes, but complacency breeds contempt. So sometimes they throw in throw in breaking changes that may render your existing config non-bootable, because why the hell not? Continue reading