Recently, one of my Supervisor 720 goes into a permanent reboot cycle. I was able to break it into ROMMON mode, but I couldn’t get it to ‘stick’ the boot settings.

Finally….

Finally, one of the other guys came and looked over my shoulder and pointed out that I was making two mistakes. Here is the correct syntax:

rommmon 2 > BOOT=bootdisk:s72033-advipservicesk9_wan-vz.122-18.SXF14.bin
rommon 3 > set
PS1=rommon ! >
LOG_PREFIX_VERSION=1
SLOTCACHE=cards;
ACL_DENY=0
PF_REDUN_CRASH_COUNT=0
RANDOM_NUM=17402343563
CRASHINFO=crashinfo_FAILED
RET_2_RTS=10:05:02 UTC Thu Jun 26 2008
RET_2_RCALTS=1214421319203
BSI=0
?=0
BOOT=bootdisk:s72033-advipservicesk9_wan-vz.122-18.SXF14.bin
rommon 4 > sync

The first mistake is that the BOOT command in the first line must be in capitals.

The second mistake I made was that I didn’t to sync the configuration register. In my defense, I have never had to do this before, but, there you go.

In turns out that the Supervisor 720 is quite different from earlier Supervisor Modules and you need to make sure that

1. you purchase Compact Flash modules
2. you need to put a second copy of IOS on the compact flash as well as on the sup-bootflash:

Cisco documentation

Surprisingly, the Cisco documentation seem to make any mention of this.