[CentOS] Setup multiple bridges for use with KVM

[Eduardo Grosclaude]

On Sat, Jan 9, 2010 at 11:15 PM, Jacob Hydeman <jhydeman at gmail.com> wrote:
> Running CentOS 5.4 x64.
>
> Have successfully bridged eth2 with br2 by following the instructions here:
> http://wiki.libvirt.org/page/Networking (under the RHEL section)
>
> Have been running several KVM VMs successfully via this bridge.
>
> I am now trying to bridge additional interfaces by using the same routine.
> Each bridge is named to correspond with the ethX device its bridged with.
>
> Example of ifcfg-eth0 script:
> DEVICE=eth0
> HWADDR=00:16:76:D6:C9:45
> ONBOOT=yes
> BRIDGE=br0
>
> then of ifcfg-br0 script:
> DEVICE=br0
> TYPE=Bridge
> BOOTPROTO=dhcp
> ONBOOT=yes
> DELAY=0
>
> This is repeated 3 times for eth0-eth2 and br0-br2.
>
> I've read somewhere that STP needs to be enabled when using multiple
> bridges. I've tried adding STP=on to the ifcfg-brX scripts but with the same
> result. Yes, brctl shows that STP is on.
>
> The original bridge eth2-br2 continues to work but I can't get any traffic
> across any other bridge. Either by dhcp or static ips.
>
> Is multiple bridges a possibility?
>
> Previous to moving to KVM I was running Xen Server on the same hardware. I
> am just trying to recreate the network setup I had. I believe Xen Server
> runs on top of a linux platform so such a thing should be possible.

I am curious as to what exactly is your topology and which is its
intended use. I have found no issues wrt STP but you seemingly need to
assign different vlans to your VM interfaces, depending on which
bridge they are attached to (i.e. roughly 1 bridge = 1 vlan).
I am confused about what interfaces are attached to which bridge in
your setup, would like to see the scripts you are using to start your
VMs...
Thank you in advance

-- 
Eduardo Grosclaude
Universidad Nacional del Comahue
Neuquen, Argentina