Ask Ubuntu is a question and answer site for Ubuntu users and developers. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I consider myself fairly avid with Ubuntu and Linux, but this one has me stumped. I built up a Xen Server using Ubuntu 12.04 as the base operating system. It has multiple domUs running on it. My home network has a statically defined network where I got all the network connectivity going peachy. The server was moved to a permanent home this morning. So, the network configuration on the main system had to change. Again, another static network, but now I can't ping the upstream gateway from the host. As the VMs use this NIC over a bridge, they too are broken. Ping responds with "destination host unreachable." I simplified the networking down to a simple static network as seen below (no bridge or anything) just to get it to work.

Here's the contents of my /etc/network/interfaces file:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static

Here's the contents of route -n          UG  100  0  0  eth0  U   0    0  0  eth0

And the results of pinging the gateway:

PING ( 56(84) bytes of data.
From icmp_seq=1 Destination Host Unreachable
From icmp_seq=1 Destination Host Unreachable
From icmp_seq=1 Destination Host Unreachable

Again, this worked in one network flawlessly (obviously with different parameters in the interfaces file). I did try using eth1 (as there are two NICS on the server (in case the MAC address got flipped on bootup). No success there. Yes, the cable is in the right port now :)

Any thoughts?

I appreciate the help!

Further investigation resulted in finding out the following characteristics. Grub gives you two main boot options after xen is installed. One for the vanilla kernel without Xen, and one with Xen. The default is to use the Xen boot configuration. If I use the vanilla kernel option, with no Xen, networking is just fine. If I use the Xen option, networking breaks. I compared the routing tables for the two setups with "route -n" and they are identical. The /etc/network/interfaces file hasn't changed. So, it must be something to do with the way the bridge is setup, or Xen performs it's network initialization. This is diving into an area I'm unfamiliar with. Can anyone give me an idea how to proceed solving this problem? Otherwise, I have to bail on Xen (which I don't want to do) and try VirtualBox instead. This is horribly frustrating.

share|improve this question

Your broadcast, network, and netmask do not agree. Using the netmask you specified, the broadcast and network addresses are not on the same subnet as the IP address and gateway you specified. You probably are using the wrong netmask, and it should be rather than .240.

share|improve this answer
Thank you for your quick response. I did some homework based on what you said. The data center gave me the IP address, gateway, and netmask. So, I would like to think they are correct. I found an IP calculator to determine the network and broadcast settings for the VLAN the data center put me up on. Network was set to and broadcast set to Still getting the same host unreachable. Is this simply finding out what those two settings need to be from the data center or is there a way to actually calculate this quickly without a ton of trial and error? – blckblttkd Dec 4 '12 at 1:08

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.