Hi!
I built a xen 3.3.0 kernel on a Debian GNU/Linux 4.0 r4a (AMD64). When 
I boot the system without xen everything works fine. When I boot it 
with xen the network is not working. Here are the outputs of `ifconfig 
-a` for the system with and without xen:
Without xen (everything is as it should be):
-----------------------------------------------------
# ifconfig -a
eth0      Protokoll:Ethernet  Hardware Adresse <anonymized>
         inet Adresse:192.168.2.105  Bcast:192.168.2.255  
Maske:255.255.255.0
         inet6 Adresse: fe80::21e:8cff:fece:7f/64 
Gültigkeitsbereich:Verbindung
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:283 errors:0 dropped:0 overruns:0 frame:0
         TX packets:45 errors:0 dropped:0 overruns:0 carrier:0
         Kollisionen:0 Sendewarteschlangenlänge:1000
         RX bytes:31321 (30.5 KiB)  TX bytes:5393 (5.2 KiB)
         Interrupt:177
eth1      Protokoll:UNSPEC  Hardware Adresse <anonymized>
         BROADCAST MULTICAST  MTU:1500  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
         Kollisionen:0 Sendewarteschlangenlänge:1000
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
lo        Protokoll:Lokale Schleife          inet Adresse:127.0.0.1  
Maske:255.0.0.0
         inet6 Adresse: ::1/128 Gültigkeitsbereich:Maschine
         UP LOOPBACK RUNNING  MTU:16436  Metric:1
         RX packets:66 errors:0 dropped:0 overruns:0 frame:0
         TX packets:66 errors:0 dropped:0 overruns:0 carrier:0
         Kollisionen:0 Sendewarteschlangenlänge:0
         RX bytes:5176 (5.0 KiB)  TX bytes:5176 (5.0 KiB)
sit0      Protokoll:IPv6-nach-IPv4          NOARP  MTU:1480  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
         Kollisionen:0 Sendewarteschlangenlänge:0
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
-----------------------------------------------------
Only eth0 is used, because eth1 is an onbord WLAN card that is 
disabled in the bios (when I use ifconfig without the -a option, this 
interface is not listed).
With xen (no network interfaces except lo and the tmpbridge which is 
not connected to any network interface):
-----------------------------------------------------
# ifconfig -a
lo        Protokoll:Lokale Schleife          inet Adresse:127.0.0.1  
Maske:255.0.0.0
         UP LOOPBACK RUNNING  MTU:16436  Metric:1
         RX packets:60 errors:0 dropped:0 overruns:0 frame:0
         TX packets:60 errors:0 dropped:0 overruns:0 carrier:0
         Kollisionen:0 Sendewarteschlangenlänge:0
         RX bytes:4660 (4.5 KiB)  TX bytes:4660 (4.5 KiB)
tmpbridge Protokoll:Ethernet  Hardware Adresse 00:00:00:00:00:00 
         BROADCAST MULTICAST  MTU:1500  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
         Kollisionen:0 Sendewarteschlangenlänge:0
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
-----------------------------------------------------
I was not able to detect the problem from the logfiles. Which further 
information do you need to detect the problem or what should I try out?
Thanks, Ingo!