You can find the MAC address for LAN1/eth0 (not the BMC MAC) via the SuperMicro IPMI interface by running the following command:
$ ipmitool -U $IPMI_USER -P $IPMI_PASS -H $IPMI_HOST raw 0x30 0x21 | tail -c 18
The eth0 MAC address will be output in this format:
00 25 90 f0 be ef
To get BMC MAC:
$ ipmitool -U $IPMI_USER -P $IPMI_PASS -H $IPMI_HOST lan print | grep "MAC Address"
or
$ ipmitool -U $IPMI_USER -P $IPMI_PASS -H $IPMI_HOST raw 0x0c 0x02 0x01 0x05 0x00 0x00