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I have a virtual box disk on my NAS so I can use it from Windows as well as Linux.
This works fine except on Windows (7) the VM sometimes freezes.
The NAS (QNAP TS-109II) occasionally sends me an e-mail about the NIC link having being down but the VM freezes appear to occur more often than that. So I suppose, these events are not correlated.

In the windows log there is a message from today at 7:15am. But I think the VM froze around 7:30 or even later.. This may have to do with it; but if yes, there must be some sort of delay between the events.

The IP address lease for the Network Card with network address 0x1234567890abc has been denied by the DHCP server (The DHCP Server sent a DHCPNACK message).

(The above is not the real MAC address; the real one is the one of my PC's NIC, not a VirtualBox network adapter.)

Do you hava any suggestions on what could be causing the freezes and why they happen on Win 7 but not on Linux?

Update: DHCP Server

The DHCP server runs on my router (Netgear WGR614v9) and is configured to supply my PC always with the same IP address. I could not find any settings regarding the lease time.
Another addition: The router is also configured to give the same IP address to the NAS device.

The NAS only supports 100MBit/s and so does the router in between it and my PC (not an ideal setup but that's another story). So Gigabit-LAN and Jumbo frames are not an issue, either.

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Can you try putting the NAS unit on a static IP and see if you encounter the same issues? Also, try turning off automatic link speed negotiation on the NAS (set it to either 100/Full or 1000/Auto for gigabit) as well as the ethernet frame size (some switches don't support Jumbo frames, but the NAS may be trying to use them).

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Putting the NAS unit on a static IP address didn't change the situation. – foraidt Jan 23 '10 at 11:48
up vote 0 down vote accepted

It looks like the DHCP server of my router is a bit weird and does things that either Windows 7 or VirtualBox for Windows cannot handle. I'm pretty confident that the errors logged by Windows are the cause of the problem. The occasional mails from the NAS were apparently sent for the same reason. Looks like not all mails came through since, well, the NIC link was down.

Luckily my NAS also can serve as DHCP server and so I disabled DHCP on my router and enabled it on the NAS. To make it work I also had to make sure that the the router is entered as the (primary) DNS server on the NAS.
On the NAS I also have the chance to specify the lease time, which I set to 7 days. Even if the NAS' DHCP server causes the same errors, they will occur much less frequently. My router seems to have it hard wired to 12 hours.

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