If I understand that correctly, this is a request to open session to IPMI. If you haven't received any response, then I'd check:

1. Do you have IPMI enabled?

Hello Martin,

you hit the point.

IPMI was not unable (anymore).

IPMI is activated by default since years in all our hosts.

But recent firmware upgrades on some of our Dell hosts, and especially on iDRAC firmwares led to the disabling of IPMI.

I'm sorry for having bothered you and the audience. Sorry for this waste of time. Thank you Dell :-\

-- 
Nicolas ECARNOT