[libvirt] networking with two hosts

[Andreas Rittershofer]

Am 26.02.2009 um 20:26 schrieb Radek Hladik:

> Andreas Rittershofer napsal(a):
>> My problem is:
>> 1.) VM1 running on host A must have network access to VM3 when VM3  
>> is running on host B by default _and_
>> 2.) when VM3 is running on host A because host B failed.
>> In some of my configurations 1.) worked but 2.) not, in some other  
>> configurations 2.) worked but 1.) not.
>> I must have missed some detail ...
>
> I do not see the problem. With the bridged scenario every VM has  
> direct access to the physical network and it is not important on  
> which host it runs. If the VMs are running on the same host, their  
> ethernet frames will just "turn around" in the bridge interface and  
> if they are running on different hosts they will go thru the real  
> ethernet.
>
> State 1)
> A: VM1
> B: VM3
>
> Eth. frames will go like this: VM1->BrA->PhysCardA->Ethernet- 
> >PhysCardB->BrB->VM3
> State 2)
>
> A: VM1+VM3
> B: x
>
> Eth. frames will go like this:
> VM1->BrA->VM3
>

NOW I've got it!
The errors in my configuration were two different network  
configurations on host A and on host B - I always thought that the  
network on host A and the network on host B must have different IP  
addresses. Now there is only on network configuration for host A _and_  
host B and everything is fine!

Thank you very much for your help!

mfg ar

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