Because this is a universalk9 image, you may need to set the :
Hold button on the front panel while powering on → Release after 2-3 seconds (when LED blinks green). This enters ROMmon mode: c3750e-universalk9-mz.150-2.se11.bin
: Addressing critical vulnerabilities to keep legacy hardware compliant with modern security standards. Because this is a universalk9 image, you may
Do not attempt to load this .bin onto a 2960, 3560 (non-E), or 3650. It will cause a boot loop or a ROMmon recovery situation. Because this is a universalk9 image