Supermicro IPMI unable to access through shared port

This is a known design "problem" with some shared IPMI access. This also affects Dell DRACs that use an Avocent BMC as well. It's just the way it is.

For some reference:

The reason one is unable to connect to the IPMI controller from the same machine through the network on this architecture is because this controller is architected in such a way that you CAN'T access the IPMI controller via its IP address from the same machine that the controller is on. This is because the IPMI controller and the motherboard SHARE a single physical ethernet port.

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The IPMI controller can access the network through eth0, and the motherboard can access the network through eth0, but the motherboard CANNOT access the IPMI controller through eth0. It MUST go through its internal motherboard connection, which is what happens when you use "ipmitool" without specifying an IP address. You cannot go through an IP connection to the controller from the same machine, but you can from any other machine that can route to it.