[Lxc-users] Networking issues with LXC

Daniel Lezcano dlezcano at fr.ibm.com
Thu Feb 11 21:37:18 UTC 2010

Michael H. Warfield wrote:
> On Thu, 2010-02-11 at 21:58 +0100, Daniel Lezcano wrote: 
>> Michael B. Trausch wrote:
>>> On 02/11/2010 03:46 AM, Daniel Lezcano wrote:
>>>> If you do not set a mac address in the container configuration file, the
>>>> kernel will choose one for you preventing duplicate mac address on the
>>>> host.
>>> Will it pick something that is static for each container?  I'd like 
>>> for each of my containers to have stable IPv6 addresses that persist 
>>> over reboots.
>> Ah, ok. That makes sense to specify a mac address.
> Just out of curiousity...  What determines the host side of the veth
> interfaces.  That looks to be a random number.  

Yes right.

> There's also a problem
> with Linux bridges that the mac address of the bridge is assumed to be
> the lowest mac address on the bridge (don't ask me why, that's just the
> way it is).

Oh, good point !

Looking around on internet, it seems some people creates a dummy 
interface with a lower mac address and assign it to the bridge.

brrr ...

> If you have your host eth device on that bridge and it's
> the bridge mac that is seen on the outside and plays in the IPv6
> autoconf game, you can get some confusion if a random interface added to
> the bridge changes the mac address for the hosts address.  I ran into
> this with OpenVZ and went back and implemented a policy of assigning MAC
> addresses with the local bit set and higher than any possible hard eth
> attach to the bridge.

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