Due to some still unknown bug, all the iLOs of two of my HP blade
enclosures became confused and stopped accepting TCP connections. This
not only made them unusable, but also prevented upgrading the firmware
to an hopefully fixed version...
My solution: reset them from the OS by running:
ipmitool mc reset cold
HP's support solution: remove and reseat each blade.
Permalink:
http://blog.bofh.it/debian/id_417