Ethernet fails to get IP from DHCP - but only in one location

With the cooperation of the network administrator, try assigning yourself an IP address manually. Does that work?

Start up in Recovery mode. In the OS X Utilities screen, select Get Help Online. A clean copy of Safari will launch. No plugins, such as Flash, will be available. While in Recovery, you'll have no access to your saved bookmarks or passwords, so make a note of those before you begin, if they're needed for the test.

Test. After testing, restart as usual and post the results.

If you couldn't connect in Recovery mode, then reinstalling won't have any effect. The cause of the problem is in the network, not in your computer.

Try a different network socket, try a different patch lead.

Are you really using Ethernet at home? Most people use WiFi at home, it is possible to have both active and WiFi might be providing the connectivity you think the Ethernet cable is. Double check you are not unknowingly using WiFi at home.

While your description makes it sound less likely, possible network related causes would be that the socket your using is segregated from the rest of the network by a VLAN setup and hence cannot communicated with the DHCP server and the rest of the network. This is common on corporate networks. Another possibility is that your network is now using a network access control system like 802.1x and your Mac is not authorised to connect. With VMware installed your Mac will show up as having multiple MAC addresses (not to be confused with Apple Mac) and this might have upset such security.

Check with your network guy that they don't block connections on MAC addresses, quite common in some networks to stop anyone just plugging devices in and getting a connection.

Sorry John, I should have read your post first before replying myself.

regards

If you really followed Linc's advice, then the problem is in the network or hardware. When you boot into recovery mode, you are using a separate operating system. Otherwise, I would think the failed proxy setup is the cause of the problem.

It may have been an ARP cache problem. Network switches use a protocol called ARP to map IP addresses to MAC address and keep a table of which MAC address is connected to which port. Normally the time such entries are stored is short enough that any problems would expire from the table fairly soon and hence resolve themselves but in this case maybe it got confused.

By using a different port it will have detected a new entry and readded it to the table. Turning the switch off and on, or using network management (if it has it) to tell it to 'flush' the ARP cache would probably have also cleared this.