root@ubuntu1:/tmp# cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
        address 192.168.1.212
        netmask 255.255.255.0
        gateway 192.168.1.1

auto xenbr0
iface xenbr0 inet dhcp
bridge_ports eth0
root@ubuntu1:/tmp#

/etc/init.d/networking restart

root@ubuntu1:/tmp# /etc/init.d/networking restart
 * Reconfiguring network interfaces...                                                          
 device eth0 is a bridge device itself; can't enslave a bridge device to a bridge device.

Waiting for xenbr0 to get ready (MAXWAIT is 32 seconds).
Internet Systems Consortium DHCP Client V3.0.6
Copyright 2004-2007 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

Listening on LPF/xenbr0/b6:94:29:83:20:9d
Sending on   LPF/xenbr0/b6:94:29:83:20:9d
Sending on   Socket/fallback
DHCPDISCOVER on xenbr0 to 255.255.255.255 port 67 interval 7
DHCPDISCOVER on xenbr0 to 255.255.255.255 port 67 interval 8
DHCPDISCOVER on xenbr0 to 255.255.255.255 port 67 interval 20

root@ubuntu1:/tmp# ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:15:17:4e:57:a8
          inet addr:192.168.1.212  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::215:17ff:fe4e:57a8/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:173120 errors:0 dropped:0 overruns:0 frame:0
          TX packets:49696 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:136107254 (129.8 MB)  TX bytes:5473454 (5.2 MB)

eth1      Link encap:Ethernet  HWaddr 00:15:17:4e:57:a9
          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
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Base address:0x2000 Memory:98800000-98820000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:50 errors:0 dropped:0 overruns:0 frame:0
          TX packets:50 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:2556 (2.4 KB)  TX bytes:2556 (2.4 KB)

peth0     Link encap:Ethernet  HWaddr 00:15:17:4e:57:a8
          inet6 addr: fe80::215:17ff:fe4e:57a8/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:173192 errors:0 dropped:0 overruns:0 frame:0
          TX packets:50264 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:139247884 (132.7 MB)  TX bytes:5977228 (5.7 MB)
          Base address:0x2020 Memory:98820000-98840000

veth0     Link encap:Ethernet  HWaddr 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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

veth1     Link encap:Ethernet  HWaddr 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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

veth2     Link encap:Ethernet  HWaddr 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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

veth3     Link encap:Ethernet  HWaddr 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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

vif0.0    Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff
          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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

vif0.1    Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff
          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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

vif0.2    Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff
          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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

vif0.3    Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff
          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
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

xenbr0    Link encap:Ethernet  HWaddr b6:94:29:83:20:9d
          inet6 addr: fe80::b494:29ff:fe83:209d/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:2178 (2.1 KB)

root@ubuntu1:/tmp# brctl addif xenbr0 eth0
device eth0 is a bridge device itself; can't enslave a bridge device to a bridge device.
root@ubuntu1:/tmp# ifconfig -a