I have a Supermicro board with IPMI set to shared mode. The issue is well-described here: http://serverfault.com/questions/560575/supermicro-ipmi-unable-to-access-through-shared-port
That is, the host can't access its own IPMI via network it it's in shared mode. However, it can access its IPMI directly, just how ipmitool does without specifying a host (-H flag).
It would be great if Zabbix could ask for IPMI directly aswell and thereby use the IPMI functionality of the board.

Thank you for your project!