Dell iDRAC devices tend to have problems negotiating with a switch port that’s at 1000mbit/auto – the device is limited to 100mbit. The quickest way to get it working is to disable auto and just go 100/Full.

/admin1-> racadm getconfig -g cfgNetTuning
cfgNetTuningNic100MB=2
cfgNetTuningNicFullDuplex=1
cfgNetTuningNicMtu=1500
cfgNetTuningNicAutoneg=1
/admin1-> racadm config -g cfgNetTuning -o cfgNetTuningNicAutoneg 0
Object value modified successfully
/admin1-> racadm racreset
RAC reset operation initiated successfully. It may take a few
 minutes for the RAC to come online again.

After a minute or so from it’s reboot it should pop right up on the network.

source: http://tacticalvim.wordpress.com/2013/03/07/disabling-autonegotiate-on-the-dell-idrac/