Hi,

Please see the prerequisites to performing ISSU:

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/XE3-5-0E/15-21E/configuration/guide/config/issu.html#pgfId-1072849

One of these is specified as follows:

Autoboot is turned on and the current booted image matches the one specified in the BOOT environmental variable. For details on how to configure and verify these, please refer to "Modifying the Boot Field and Using the boot Command".

The error you are experiencing simply states that the Boot field of your config-register is NOT set for autoboot. The fatory default for your box is 0x2101 (you can check via the "sh ver" command) the prerequisites ask the last nibble to be 2 ie. 0x...2 (please note that while some customers like it set to 0x2102 according to the configuration guide the recommended value for your box is 0x0102).

Please be aware that there are implications to this change and you should both follow the ISSU procedure carefully and also understand what you are doing.

Good luck!

Best regards,

Antonin