[Lxc-users] Networking issues with LXC

Michael H. Warfield mhw at WittsEnd.com
Thu Feb 11 21:21:23 UTC 2010

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.  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).  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.

> Maybe this script can help you to generate mac address automatically 
> with the container configuration.
> http://mediakey.dk/~cc/generate-random-mac-address-for-e-g-xen-guests

Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
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