Symptom
Occasionally, during a ROMMON firmware upgrade, we can encounter a failed checksum, leading to the failure of the upgrade process:
csg-rtp-ovld#up ro fi bootflash:isr4400_dev_rommon_SSA.pkg r0
Chassis model ISR4451-X/K9 has a single rom-monitor.
Upgrade rom-monitor
Target copying rom-monitor image file
Booted : 0
Selected : 0
Reset Reason: 1
Secure upgrade of the ROMMON image will occur after a reload.
Copying ROMMON environment...
262144+0 records in
262144+0 records out
262144 bytes (262 kB, 256 KiB) copied, 0.675992 s, 388 kB/s
Switching to ROM 1
Updating ROMMON environment...
262144+0 records in
262144+0 records out
262144 bytes (262 kB, 256 KiB) copied, 16.6496 s, 15.7 kB/s
262144+0 records in
262144+0 records out
262144 bytes (262 kB, 256 KiB) copied, 1.41592 s, 185 kB/s
FAILURE: ROMMON Variable data failed verification check.
Conditions
This has mainly been seen on ISR 4k routers, though other prerequisite conditions are unknown.
Workaround
This issue doesn't occur every time, so subsequent upgrade attempts may be successful.
