This took us some time to figure out… we had a brand new Dell Latitude E6420 over here, and it refused to connect with our LAN when we hooked it up to a Dell PowerConnect 5548 Switch.
- Direct connections between the laptop and the PowerConnect switch were refused: No DHCP lease, no traffic, sometimes Network link was just down
- The laptop could connect to this switch if we used a small switch/hub between the laptop and the Powerconnect Switch
- Direct connections worked if we booted from a live CD (Ubuntu)
- Direct connections did not work on Windows Xp and Windows 7 (fresh installs)
- Network cable was not damaged
- Laptop NIC (Mainboard) has been swapped by Dell, so we made sure this one was not faulty, too
- We experienced the same behaviour with a second brand new Dell Latitude E6420