There is a known Cisco bug, ID CSCvf24186, that can affect 2960X series switches when upgrading the IOS software. The issue is not supposed to occur when upgrading to currently recommended IOS versions. Recently, when an upgrade was performed on a 2960X, as a trial before pushing out a company-wide upgrade for a customer the issue occurred. This was an upgrade to the recommended version that was only two minor releases ahead of what was currently on the switch.
The result of the bug is the switch will not fully load and will need be sent back to Cisco for replacement. Booting the switch to ROMMON will not resolve the issue. Even though you can load a different IOS version, or even attempt to go back to the previous working version, the switch will not fully load no matter the version of IOS installed.
This issue, along with an existing bug on older IOS for the 2960Xs that can cause POE to stop working if not updated requiring an RMA, creates a difficult dilemma. Failing to upgrade the IOS can result in POE no longer functioning that, if required, will create the need for a new switch, while upgrading can potentially cause the entire switch to quit functioning.
At this time, if a 2960X is to be upgraded, it should be done with full understanding that the switch may be lost, and the need for an RMA replacement resulting in significant downtime is possible. For that reason, it is not recommended to push IOS upgrades to multiple switches at once. These switches should be upgraded individually with a replacement available to be inserted incase of failure before the outage begins impacting your business. Since many customers do not have spares on hand, and the RMA replacement takes 24 hours or more to arrive depending on the support level, this can be very difficult to accomplish.
Cisco considers this bug resolved when updating to the most recent IOS version. However, experience has shown it may still occur. ZeroDay recommends this extra precaution as to alleviate frustrations brought on by the possibility of a prolonged outage.
This bug can have devastating repercussions if not handled properly. If you have experienced complications due to this bug, contact ZeroDay Technology Solutions.