Migration, Upgrade, and Downgrade Instructions
This section contains the procedure to upgrade Junos OS, and the upgrade and downgrade policies for Junos OS. Upgrading or downgrading Junos OS can take several hours, depending on the size and configuration of the network.
Upgrade and Downgrade Support Policy for Junos OS Releases and Extended End-Of-Life Releases
Support for upgrades and downgrades that span more than three Junos OS releases at a time is not provided, except for releases that are designated as Extended End-of-Life (EEOL) releases. EEOL releases provide direct upgrade and downgrade paths—you can upgrade directly from one EEOL release to the next EEOL release even though EEOL releases generally occur in increments beyond three releases.
You can upgrade or downgrade to the EEOL release that occurs directly before or after the currently installed EEOL release, or to two EEOL releases before or after. For example, Junos OS Releases 12.3X48, 15.1X49, 17.3, and 17.4 are EEOL releases. You can upgrade from Junos OS Release 15.1X49 to Release 17.3 or from Junos OS Release 15.1X49 to Release 17.4. However, you cannot upgrade directly from a non-EEOL release that is more than three releases ahead or behind.
Upgrade from Junos OS Release 17.4 to successive Junos OS Release, is supported. However, you cannot upgrade directly from a non-EEOL release that is more than three releases ahead or behind.
To upgrade or downgrade from a non-EEOL release to a release more than three releases before or after, first upgrade to the next EEOL release and then upgrade or downgrade from that EEOL release to your target release.
For more information about EEOL releases and to review a list of EEOL releases, see https://www.juniper.net/support/eol/junos.html.
For information about software installation and upgrade, see the Installation and Upgrade Guide for Security Devices.
For information about ISSU, see the Chassis Cluster Feature Guide for Security Devices.