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When I boot my Mac up with a network cable plugged in (connected to my router), the network works fine. But after the connection has been physically separated once (and the cable reinserted), it fails to get an IP address from the router (via DHCP). Mac OS just assigns a seemingly random IP address, and I can't access the internet anymore. After a reboot (with the cable plugged in), it works again.

This seems to be a Mac-only, cabled-only problem. WiFi works fine, and every other computer I tried (Windows & Linux notebooks) doesn't have the problem.

I'm using OS X Lion, and the Router is a D-LINK DIR-615, if it matters.

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You could try to go to network (when its failing your dhcp) and switch off your Ethernet connection. Then switch it on and see if it works. At-least it saves you a reboot. – Rogier Aug 21 '12 at 12:17
@Rogier: Thanks, I'll try that the next time it happens. – jdm Aug 21 '12 at 12:22
Also try a different cable (don't expect its your problem), but worth trying. What i can think is that for some reason the IP address is not released on the router, and 'it' thinks your still connected. You could play a bit with the expiration times. – Rogier Aug 21 '12 at 12:27

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