[CentOS-virt] proper bridging technoque

Thu Nov 21 22:42:02 UTC 2013
aurfalien <aurfalien at gmail.com>

On Nov 21, 2013, at 2:36 PM, Digimer wrote:

> On 21/11/13 17:32, aurfalien wrote:
>> On Nov 21, 2013, at 2:24 PM, Digimer wrote:
>>> I'm not sure what you are asking.
>>> You should not see the vnetX devices from the VM (or even the VM's
>>> definition file). They're created as needed to link the VM's interface
>>> to the bridge. Think of them as simple network cables.
>>> Some of the formatting isn't showing well on my mail client (text only),
>>> so I am having a little trouble parsing some of the data...
>>> If the VMs are using br6, then you see that it's already at 9000, so you
>>> should be able to use 9000 from inside the VM as well. Trick is, the
>>> vnetX devices are connected to the br0 bridge instead, which is set to
>>> 1500 because eth0 is still 1500. So at this point, the VMs are
>>> traversing br0, not br6.
>>> As for 'virbr0', that is libvirtd's default NAT'ed bridge. I don't
>>> recommend using those. I usually destroy them, personally.
>>> So to fix your problem, you need to tell the VMs to use br6. If you want
>>> to use jumbo frames on br0, you need to increase the MTU of eth0.
>>> Remember that the bridge will use the MTU of the lowest connected device.
>> So far my current VMs that work, I see there network as;
>> Host device vnet 0 (Bridge 'br0')
>> I do not see a;
>> Host device vnet# (Bridge 'br6')
>> My ints of interest are set to jumbo so thats not a prob.  I think the prob is that I am missing the vnet bridge device for eth6.
>> So I'm curious why its not there and how do I create it?
>> - aurf
> I can't speak to the tools you are using, but I can say that this is
> where the bridge is defined in the VM's XML definition file:
> ====
> [root at an-c05n01 ~]# cat /shared/definitions/vm01-win2008.xml |grep vbr
> -B 2 -A 5
>    <interface type='bridge'>
>      <mac address='52:54:00:8e:67:32'/>
>      <source bridge='vbr2'/>
>      <target dev='vnet0'/>
>      <model type='virtio'/>
>      <alias name='net0'/>
>      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
> function='0x0'/>
>    </interface>
> ====
> Try changing: <source bridge='br0'/> -> <source bridge='br6'/> and
> restart the VM.

It already has the source bridge as br6.

But I think I need to have a;

vnet6 to br6 relationship defined somewhere.

Right now I only see;

Host device eth6 to br6 but I need vnet6 to br6 or something like that.

Currently, while my guest VM sees its int via ifconfig, it cannot get an packets to/from.

This is why I feel the need for a vnet to br6.

- aurf
> -- 
> Digimer
> Papers and Projects: https://alteeve.ca/w/
> What if the cure for cancer is trapped in the mind of a person without
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