I've been running my QNAP 469L with Debian (Wheezy deb7u3) for a few months. Yesterday I upgraded the memory to 4 GB. The system boots fine, but since the upgrade, I'm not able to connect the server to my router (a TP-Link WR941ND).

My configuration:

• The router runs a DHCP server (192.168.67.100 and up), with a preconfigured ip address for the QNAP (192.168.67.10). The router is on 192.168.67.1.
• As said, Debian is installed on the QNAP (which can be regarded as a normal computer).
• Networking hardware on the QNAP: Intel PRO/1000 Network Connection using the e1000e kernel module.

This is what I have tried so far:

• Replace the network cable (tried 3 different cables on different router ports).
• Check for messages from the kernel: dmesg | grep eth. Besides the normal hardware messages I get a ADDRCONF(NETDEV_UP): eth0: link is not ready for each call to ifup.
• Manually restart the network sudo server networking restart
• Check sudo ifconfig (eth0 is up, but no ip addresses).
• Check the /etc/network/interfaces which has (besides the loopback device) an allow-hotplug eth0 and iface eth0 inet dhcp, which is afaik the default Debian configuration.
• Since the server has two ethernet ports, I checked if I'm using the right port (checked the hardware address that ifconfig reports for eth0 is the same as the hardware address that is in the preconfigured ip address for the server in the router.
• Do a manual sudo ifdown eth0 && sudo ifup eth0 with no results (but an extra ADDRCONF(NETDEV_UP): eth0: link is not ready in the kernel log)
• Do a dhcp request dhclient -v eth0: for about a minute requests are send (according to the terminal) and at the end I get a No DHCPOFFERS received. No working leases in persistent database - sleeping..
• Check the router system log if DHCP requests are received. I see them for some devices (my Mac, my iPhone) but not from the QNAP. The log entry looks like: DHCPS:Recv REQUEST from 84:85:06:07:75:6A and then a DHCPS:Send ACK to 192.168.67.101. There are no records from the QNAP's hardware address.

So the two error messages that I do get are: ADDRCONF(NETDEV_UP): eth0: link is not ready for every ifup and No DHCPOFFERS received. No working leases in persistent database - sleeping. for every DHCP call.