I would like to upgrade Cisco 3750x from 12.2(55)SE7 to 15.2.4E7 MD and I would like to confirm if we can jump from 12.2 to 15.x version?
Also please advise if anybody saw any issues going to this new version.
I recommend you make a gradual update until the IOS you want.
Sometimes, a direct jump gets compatibility problems.
You could start updating to the highest version of IOS 12.2
Then jump to the lowest version of IOS 15.2
Finally, upgrade to the newest version.
Remember to check that the versions are always compatible with the hardware of your device.
This is the latest IOS posted and also suggested by Cisco.
You should be fine as long as you have enough memory and flash space which is 256/64
Yes, for the smaller switches (3560, 3750, 3750x, 3850, etc..) the bootstrap will be upgraded as part of the IOS. Just be prepared for a long time for the device to load. I think it takes about 17 minutes for the new IOS to load. So, don't panic if it takes a long time to reboot. Also, make sure your maintenance window is long enough to accommodate the reboot time and verification.
And one more thing, make sure to back up the config before upgrading.