Just got this machine and want to use the IPMI. Each node has a dedicated IPMI port. I have enabled it in BIOS and assigned it an IP address. Even directly connected to it both with and without crossover gets me exactly zilch. The IPMIView utility cannot find it. I get this feeling I am missing something obvious but I cannot find anything in the manual that I am missing.
It sounds like you are plugging/unplugging the cable to the dedicated LAN port.
Certain BMC chips will only activate the dedicated LAN port if an active network cable is plugged into the port before you activate the BMC (at first power-on or cold reset). On a recent install, I had to make sure that the network cable was plugged into an active network switch (e.g. the data link layer had to be active. Electrons had to be flowing over the wires).
You might need to perform a cold boot. Last week, a BMC only worked when I unpluged the power cables, and allowed the capacitors to drain.
Then turn it on, and the BMC will detect that the dedicated LAN port is active. Watch for the link light.
This is the case for many Supermicro servers which use the Nuvoton WPCM450 Controller. However, it appears that your X8DTT-HEF+ is running with a different chip, so the procedure might be different.
Failover/Dedicated/Shared LAN setting, unfortunately nonstandard and not available via ipmitool expect by barely documented raw commands; can be set from the web interface (access it via the main lan port; if the setting is failover then either boot the box ICE COLD (ermove physical power) or try ipmitool mc reset cold, both with a working switch on the IPMI LAN port.