netdev - Re: Bridge connectivity interruptions while devices join or leave the bridge

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Message-ID: <cc7b7c8d-16bb-18a5-4b3a-91690acf47dc@techfak.uni-bielefeld.de>
Date:   Wed, 19 Sep 2018 13:00:15 +0200
From:   Johannes Wienke <jwienke@...hfak.uni-bielefeld.de>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     netdev@...r.kernel.org
Subject: Re: Bridge connectivity interruptions while devices join or leave the
 bridge

Dear Ido,

On 9/19/18 12:07 PM, Ido Schimmel wrote:
> On Wed, Sep 19, 2018 at 11:10:22AM +0200, Johannes Wienke wrote:
>> Can someone explain what is happening here and why adding and removing
>> devices to a bridge results in the connectivity issues? How to avoid
>> this behavior? I'd be glad for any hint on that.
> 
> The MAC address of the bridge ('brtest' in your example) is inherited
> from the bridge port with the "smallest" MAC address. Thus, when you
> generate veth devices with random MACs and enslave them to the bridge,
> you sometimes change the bridge's MAC address as well. And since the
> bridge is the default gateway sometimes packets are sent to the wrong
> MAC address.

Thank you very much! This was the important hint and solves the issues.

This behavior of inheriting the mac address is really unexpected to us.
Is it documented somewhere?

Kind regards
Johannes
-- 
Johannes Wienke, Researcher at CoR-Lab / CITEC, Bielefeld University
Address: Inspiration 1, D-33619 Bielefeld, Germany (Room 1.307)
Phone: +49 521 106-67277



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