I am having an ethernet connectivity problem, where my iMac and Mac Book Pro cannot connect to my home lan when I plug the ethernet cable directly into their ethernet ports. However, if I plug the ethernet cable into an apple usb to ethernet adaptor and connect via the iMac or MBP USB port, every thing works fine. My suspicion is that something with the DHCP handshake is timing out when connected via the computers ethernet adapter as opposed to using apples USB to ethernet adaptor. I am trying to use Devolo dLan powerline adaptors to run an ethernet connection to a room where I have poor wifi signal. Ideally I would like to locate an airport express and an iMac in the room. I have both Devolo dLan 500 and dLan 200 adaptors. I first was testing the connections using a MacBook Air where I had to use the USB to ethernet USB adaptor. Using iperf, I was able to determine that I was typically able to get in excess of 120Mbits/s to the room in question. Using a weak wifi signal, I was only able to get Kbits via WiFi. My plan was to attach an airport express to the Devolo dLan device and then the iMac to the spare ethernet port on the airport express. This way I could use the iMac and also extend WiFi coverage to that area of my home. I initially tested my intended setup with a MacBook Air. Everything worked just fine. However, when I attached the ethernet cable to my Airport Express it did not appear to see the ethernet connection. I then tried my iMac, it too thought there was a problem with the ethernet adaptor. Initially, failing to get an IP address and eventually assigning itself something like 169.254.127.40 and mask 255.255.0.0. On subsequent tries it will assign a 169.254.x.y where x and y have different values than the earlier tests. At first I thought I might have a cable problem. I verified the cable was good. To confirm it wasn't a problem with the iMac, I tried my Mac Book Pro. However, it too had the same behaviour as the iMac. Since it was working with the Mac Book Air, I then tried the using the USB ethernet adaptor with the iMac and the Mac Book Pro. They both recognize the home network and operate smoothly over it when the Devolo dLan device is connected to them via the Apple USB to ethernet adaptor. But they do not recognize the network when attached via their ethernet ports. You might ask why not use the USB adaptor. The problem is it can only be attached to the iMac it does not allow me to extend my wifi coverage. Ideally I would like to do both. Any thoughts or suggestions as to why my ethernet connection would only work with the USB adaptor?