Software Maintenance Upgrade (SMU)
The Software Maintenance Upgrade (SMU) is a package that can be installed on a system to provide a patch fix or security resolution to a released image for a specific defect in order to respond to immediate issues. It does not contain new features.
Some of the caveats of the SMU are:
- Provided on a per release, per component basis and is specific to the platform. SMU versions are synchronized to the package major, minor, and maintenance versions they upgrade.
- SMUs are not an alternative to maintenance releases. All defects fixed by SMUs are then automatically integrated into the upcoming maintenance releases.
- The Cisco IOS XE platform internally validates the SMU compatibility and does not allow you to install non-compatible SMUs. This is based on rules/limitations for a SMU change-set.
- An SMU provides a significant benefit over classic IOS software as it allows you to address the network issue quickly while reducing the time and scope of the testing required.
- SMU is a method to fix bugs in an existing release, and allows the application of a PSIRT fix in an existing release
- SMU is NOT an upgrade path from release X to maintenance release X.1
- SMU is NOT an upgrade path from release X to release Y
The device only supports “Hot Patching”. This means:
- The running image is modified in-place or in-service
- This avoids downtime and interruption of service
- The updated code to fix the defect is written in a different location, and where the patch redirects the program run