Ethernet cannot see RTA1025W modem (wi-fi can)

At home I have a Dynalink RTA1025W DSL modem.

• MBP can obtain IP via WiFI


• MBP cannot see modem or get IP via ethernet.


• Ubuntu/Win7/Win8 can get IP via the same ethernet cable & modem.

At work:

• MBP can see the LAN and obtain IP via ethernet using the same USB ethernet adapter.

When I'm at home and I attempt to get an IP address via ethernet, I open the network preferences | USB Ethernet | Advanced | Renew DHCP Lease. It thinks about it for a second, then puts focus in the box titled "DHCP Client ID", as if it expects me to type something.

The status remains "cable unplugged". Either the cable for USB Ethernet is not plugged in or the device at the other end is not responding.

If I try to ping my router's address (192.168.1.1) no route is found.

I have tried many different cables, all otherwise known to be working.

Occasionally, the network config will decided to allocate a self-assigned IP, which is not helpful. It does this at random times without any prompting from me.

When I touch the USB ethernet adapter dongle it is warm (this may be normal).

I have tried the following without success:

• deleting and re-adding the USB Ethernet interface


• creating a new network "location"


• removing the file com.apple.plf.plist


• assigning manually an IP from the valid range


• safe boot (problem occurs in safe boot)


• SMC reset & wait 10 mins


• PRAM reset


• removing NetworkInterfaces.plist and preferences.plist


• removing SystemConfiguration/*


• trying a different cable


• trying a different ethernet port on same modem


• trying a different USB port on MBP

Any other advice?