[libvirt] networking with two hosts

[Andreas Rittershofer]

Am 25.02.2009 um 23:28 schrieb Radek Hladik:

> Andreas Rittershofer napsal(a):
>> Am 25.02.2009 um 00:11 schrieb David Lutterkort:
>>> On Tue, 2009-02-24 at 14:25 +0100, Andreas Rittershofer wrote:
>>>> Task 1.) Each VM must have network access to each other VM and to  
>>>> the
>>>> outside.
>>>> Task 2.) When one host fails, all VMs are running on the remainig  
>>>> host
>>>> and 1.) must still be fulfilled.
>>>>
>>>> Does somebody has any hints about realising this scenario with  
>>>> libvirt
>>>> and KVM?
>>>

Thank you for your answer.

>
> Basically the idea is like this. You have your hosts on one ethernet  
> segment. You create bridge on each hosts and put hosts physical  
> adapter into it (lets call the bridges BrA and BrB). The bridge  
> behaves like a virtual ethernet switch. You should configure IP on  
> the bridge not on the physical interface itself. And now if you add  
> any other adapter into the bridge, it will act as if it is directly  
> on the ethernet. This has been used for bridging two or more  
> ethernet segments into one for a long time.

This was not the problem and runs fine.

>
> If you setup your VMs correctly (see the wiki page for details),  
> libivirt will create hosts virtual adapter and add it to the bridge.  
> For example for VM1 running on A it will create i.e. vnet1 and add  
> it to the bridge BrA. The virtualized interface in the VM1 will have  
> direct access to the ethernet segment. It can have IP address from  
> the same range as the hosts, etc...

This was not the problem too and runs fine too.

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 ...

mfg ar



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