I've been hearing of Xen for a while now and wanted to try it first hand. I've converted our gateway to Xen and installed two virtual machines on it, the gateway (routing/fw) still runs in Xen0, but external DNS and internal DNS/DHCP run on a virtual machine. It wasn't hard to setup and it works nicely. I needed to compile my own kernel images for Xen since the images that come with it do not have firewall or IPv6 which I needed.

All in all I like Xen, it looks like a good way to keep several machines on the same hardware and the 2Ghz P4 runs everything nicely with no noticeable service degradation.

In the process I found how to configure bridges in Debian, a simple thing apparently, just whip up a name and say:

   iface br-lan iface static
       address 10.4.4.4
       netmask 255.255.255.0
       bridge_ports lan0

And you get a bridge that has lan0 has the only interface under it. This works nicely with Xen which adds interfaces to bridges when you start the virtual machine. Notice that lan0 doesn't anymore need any definition of IP, br-lan takes that definition now. Also notice that you really want to use ifrename to make interface names consistent and avoid worrying if on this boot you have eth0 as wan or as lan.

Next stage, find how to backup the images from under Xen so that we can move the whole thing to another machine with ease. I know about Xen live moving of an image, but it doesn't help after a machine crashed. Current thinking is just to rsync the file systems, but these will need an fsck on boot. Ideas?