[libvirt] macvtap nt working on kvm

[Amit Tewari]

Hi,
Actually macvatap doesn't work with bridge. So once the physical device
is attached to a bridge, a macvtap attached to that device no longer
works.
In my case there is no bridge on the interface. but still guest os is
not able to get ip address.

Is there no support for macvtap on red hat 6.1 x_86 platforms?
-----Original Message-----
From: libvir-list-bounces at redhat.com
[mailto:libvir-list-bounces at redhat.com] On Behalf Of Laine Stump
Sent: Thursday, December 15, 2011 2:31 AM
To: libvir-list at redhat.com
Subject: Re: [libvirt] macvtap nt working on kvm

On 12/14/2011 02:26 PM, Stefan Berger wrote:
> On 12/14/2011 07:40 AM, Amit Tewari wrote:
>>
>> Hi all,
>>
>> My test environment
>>
>> Host os=rhel6.1
>>
>> Guest os = rhel6.1
>>
>> Libvirt=0.8.7
>>
>> Kvm hypervisor
>>
>> I have made this entry in guest xml file
>>
>> <interface type='direct'>
>>
>> <source dev='eth0' mode='bridge'/>
>>
>> <model type='virtio'/>
>>
>> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' 
>> function='0x0'/>
>>
>> </interface>
>>
>> Now when I start the guest
>>
>> *#virsh start guest*
>>
>> Following macvtap0 is created on host and is shown below
>>
>> #*ip link show macvtap0*
>>
>> 51: macvtap0 at eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc 
>> mq state UNKNOWN qlen 500
>>
>>     link/ether 52:54:00:55:AE:B5brd ff:ff:ff:ff:ff:ff
>>
>> but when the guest is up and I try to perform
>>
>> **
>>
>> *# ifup eth0*
>>
>> *eth0 has same mac address as that of macvatap0 that is 
>>  52:54:00:55:AE:B5*
>>
>> **
>>
>> *due to this guest is not able to get dhcp address nor static ip 
>> address is working*.
>>
>> Please let me know how macvtap work on kvm.
>>
>
> I have tried your setup on my machine with the following host 
> configuration:
>
> # brctl show
> bridge name    bridge id        STP enabled    interfaces
> br0        8000.001a64d00016    no        eth0
> virbr0        8000.000000000000    yes
>
> If I use the configuration as you have shown it doesn't work for me, 
> either. However, if I use
>
> <source dev='br0' mode='bridge'/>
>
> then it works as expected. Do you happen to have a similar 
> configuration on the host with the interface the macvtap device wants 
> to use as 'source' being bridged?

Interesting. So you're saying that once the physical device is attached 
to a bridge, a macvtap attached to that device no longer works? That's 
useful to know :-)


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