Best way is to reset to defaults and clear FRU&LAN with SuperMicro native tool, like so:
(All this may take a few seconds to take effect, so wait between commands!)
Now turn off the DHCP setting restored from factory defaults with
./ipmicfg-linux.x86_64 -dhcp off
then, restore your network settings with:
./ipmicfg-linux.x86_64 -m $IP_ADDRESS
./ipmicfg-linux.x86_64 -k $NETMASK
./ipmicfg-linux.x86_64 -g $GATEWAY_IP
I've noticed, that sometimes, you need to reset BMC unit for it to take effect. Just today, was unable to ping my server's IPMI IP address set via ipmicfg utility until after BMC reset:
You'll have to configure the IP/Netmask/Gateway again with the same tool, but this is the only way I could make it work.
OpenIPMI and IPMITools did not work for me on Debian Squeeze. I've tried resetting the password, cold resetting BMC, to no avail. However, they are good for setting IP and reading sensor data.
You can get the appropriate version for your OS from SuperMicro FTP: