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Date: Thu, 24 Feb 2011 08:50:18 +0100
From: Jan Kiszka <jan.kiszka@siemens.com>
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Subject: Re: [Qemu-devel] Re: Network bridging without adding bridge with
	brctl, possible?
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To: Gerhard Wiesinger <lists@wiesinger.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Arnd Bergmann <arnd@arndb.de>

On 2011-02-24 07:49, Gerhard Wiesinger wrote:
> On Wed, 23 Feb 2011, Jan Kiszka wrote:
>> Right, but if I set IP(eth0) == IP(macvlan0), I'm able to communicate
>> between macvlan0 and mactapX, thus between guest and host. Just
>> re-checked here, still works (after resolving the usual MAC address mess
>> I caused by configuring manually).
> 
> Thnx for the tipp.
> 
> Did you use MAC(eth0) == MAC(macvlan0) or MAC(eth0) <> MAC(macvlan0) to 
> get it to work?

The latter (I just let macvlan/tap choose their MACs).

> 
> OK, that should be possible because of the layer2 "split brain" 
> implementation of macvlan/macvtap between lower interface (e.g. eth0) and 
> mavlan*/macvtap*. Therefore the macvlan*/macvtap* interfaces see only each 
> other and the outer world/eth0 is another distinct layer2 domain.
> 
> My only concern is about layer3 (IP) and same IP address on the same host. 
> Because of the "split brain" there shouldn't be any problem from the 
> macvlan*/macvtap* point of view and also from the eth0 outside world view.
> 
> But from the view of "localhost"/iptables/routing the kernel sees 2 
> identical IP addresses. Which one is used on a local ping or local 
> connect?

None of both, rather the lookback interface.

Jan

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