When performing ISSU on Cisco 4500 switches running IOS XE, the first step to do is to issue the issu loadversion command. If the switch refuses to perform this command with the following error:
#issu loadversion 3 bootflash:cat4500e-universalk9.SPA.03.04.00.SG.151-2.SG.bin 4 slavebootflash:cat4500e-universalk9.SPA.03.04.00.SG.151-2.SG.bin
% Active Boot variable is invalid
make sure the configuration register is set to 0x2102:
#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
(config)# config-register 0x2102
Make sure you reload both supervisors before proceeding. You can check the current value of each supervisor’s configuration register using the show redundancy command.
