If the onboard LAN chip is Intel 82563EB/82575EB, MCP 55 Pro then the IPMI Mac address must be different then the onboard LAN1 (Eth0). You need to use the MAC address from IPMI card.
If the onboard LAN chip is Intel 82573, 82546 then the IPMI MAC address must be same as onboard LAN1 (eth0).