Types of Releases
Cisco IOS XR software model has three types of software releases. The software images are available for download at the Cisco Software Download page.
Feature Release
A Feature Release (FR) contains new features and support for new hardware. Feature releases have the X.X.1 (dot one) designation. For example, releases 24.1.1 and 24.2.1 are feature releases. The list of features added to a feature release is provided in the Release notes along with the installation instructions and dependencies.
Maintenance Release
A maintenance release is the primary mechanism to deliver groups of critical bug fixes to the software feature releases.
SMUs Release
A Software Maintenance Unit (SMU) is a fix that is provided until the End of Maintenance (EoM) of the release. The fix is
also committed into the next shipping release. SMUs are posted under Cisco IOS XR Software Maintenance Upgrade
on the Cisco Software Download page. Each SMU is customized for a specific software release.
For more information on release numbering, types of releases, and their timelines, see Software Lifecycle Support Statement - IOS XR.