Configuring bridges to use with KVM

[carlopmart]

Hi all,

  I have a problem with an ubuntu lucid 10.04 server used for KVM virtualization. My 
problem appears when I try to configure an "empty" bridge in /etc/network/interfaces 
file. For example, with a RedHat based distro (RHEL, CentOS) I can create a config 
file ifcfg-br20 like this:

DEVICE=br20
TYPE=Bridge
ONBOOT=yes
DELAY=0
STP=off
NM_CONTROLLED=no

  and then network startup script creates an empty bridge without bind any physical 
interface. I have tried same procedure to configure several empty bridges under 
ubuntu without luck:

auto intprodif
iface intprodif inet static
	bridge_stp off
	bridge_fd 9
	bridge_hello 2
	bridge_maxage 12

  When i try to start this bridge with "ifup intprodif" command returns me this error:

carlos at silmaril:~$ sudo ifup intprodif
Don't seem to be have all the variables for intprodif/inet.
Failed to bring up intprodif.

  How can I define an empty bridge without binding any physical interface into it??

  Many thanks.

-- 
CL Martinez
carlopmart {at} gmail {d0t} com