[CentOS] weird issue with qemu-kvm network...

Fri Feb 1 22:56:49 UTC 2013
skull <skull17 at gmx.ch>

Am 01.02.2013 23:39, schrieb James Hogarth:
>> Does anyone have an idea how to recreate the default virbr0?
>> Is it doable via virsh? I don't have a DE installed on this server, so
>> no virtual-manager. I am willing to go that far if it's worth it though.
>>
> You don't need a DE for that just yum install xauth virt-manager and ssh -X
> to forward it to your local X server.
>
> Although I do a fair amount from virsh and editing XML if you don't use a
> cluster manager/tool/IaaS like ovirt, openstack, archipel etc virt-manager
> is too useful not to have - especially to get console access to VMs nicely.
>
> I'm home now but if you're struggling on the bridge part come Monday send
> me a mail and I'll send you my server network configs to give you a start
> on this.
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>
I guess it's better to communicating this over the list, in case someone 
runs in the same problem :)

What i did in terms of network changes was the following script. It's an 
old one i used when i didn't work with virsh, because i followed an old 
tutorial for kvm-qemu on CentOS 5.
It basically creates a new bridge called bg0, creates a tap0 interface, 
and connects eth0 and tap0 to the bridge.
(comments ommited)

  22 chown root:kvm /dev/net/tun
  23 chmod 0660 /dev/net/tun
  24
  25 service libvirtd stop
  26 service httpd stop
  27 service vsftpd stop
  28 service named stop
  32 brctl addbr br0
  35 ifconfig eth0 0.0.0.0
  38 brctl addif br0 eth0
  41 ifconfig br0 192.168.2.253 netmask 255.255.255.0 up
  44 route add -net 192.168.2.0 netmask 255.255.255.0 br0
  47 route add default gw 192.168.2.1 br0
  50 tunctl -u root -g kvm -t tap0
  58 ifconfig tap0 up


so i ran this script and tried to use the tap0 the xml from the vm.
it didn't work (yeah i am not that smart in terms of bridges, i know i 
am not getting it 100 percent ;) )
but i didn't touch virbr0 at all.
it even showed up as usual when i did a "brctl show all"
and either eth0 or tap0 were connected in any way with it.

after the restart virbr0 was gone.

If you want to have more logs etc just ask away.