Hello Volker The iDRAC may have switched to shared mode. Connect network cables to the integrated NIC to see if you can connect to it from there. If that does not allow a connection then I would put the external video back in and boot to the OS. Use RACADM commands or OpenManage Server Administrator to find out what the current iDRAC settings are, and to find out if it is coming online. If the iDRAC is not coming online then you should receive an initialization failure during boot. It sounds like the integrated video controller has failed. The iDRAC console will not work without the integrated video. The iDRAC connection issues are likely just a setting/configuration issue that occurred while troubleshooting the video issue. Thanks
Took T610 out of service for a planned hardware upgrade.  Been managing it via iDRAC flawlessly for 3 years. Once on the bench there was no on-board video signal. I tried 2 different working monitors. At boot time the monitor registers a signal at first, but at the time it should post the memory test the monitor goes into power save mode. So I accessed it via RAC and configured the BIOS for an external video card, a 1xPCIe, with no problems. Booted to a Win7 on an SSD and installed 5 or 6 different firmware upgrades via Dell Command 2.0. Since I need a working RAC I switched the BIOS video settings back to internal.   Well -, now I don’t have internal video nor does the RAC ping any more. I figured that the firmware reset the iDRAC’s  fixed IP to its default, so I also tried default 192.168.0.120. I also removed reset the BIOS via the on board jumper. The front panel reports the RAC IP as how I configured it before the firmware upgrades. I re-seated the iDRAC6 Enterprise adapter and the single CPU and all DIMMS. I have a second CPU and DIMMS and additional drives that I have not installed yet. And I just checked that the 3 year warranty ended December 2014. What am I missing? And thanks in advance for any help. Volker
PowerEdge T610 no video / iDRAC issue