Totally random off the cuff... I've been fighting with an EX 4S server for the last week, trying to set up Xen under Debian Squeeze... anyone got some rock-solid instructions which they know work? I've tried both my own recipes and various tutorials on the web, but so far no luck. I managed to get Xen sort of working at one point, but then the networking wasn't working. I'm about ready to start throwing things out the window...
Last I checked Squeeze had a fairly straightforward Xen 4.0 package. I did have trouble with dropped packets, but I was doing some pretty complex stuff and it was already fixed upstream.
How exactly are you trying to setup networking? Bridged, routed, NAT on dom0 vs domU?
These two pages might help you, though both are slightly out of date:
Do you need debian?
If not,
1 - Ask for a LARA install of Xen Server (20€ IIRC).
2 - Request an additional IP with MAC address
3 - Change the MAC address of your VM on XenCenter
