Beginning in Release 21.5.R1, the NISH client supports up to two prior SR OS major releases. This backwards compatibility is effective from SR OS Release 20.10.R1. As a hypothetical example, the NISH client instance with a version number 23.5.R1 supports SR OS Release 21.2.R1 and later.
The NISH client ensures that the SR OS version of the device that it connects to conforms to the supported release interval. If the SR OS version is outside the supported range, the client fails to connect and provides an error message.