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Re: [Xen-users] Constructor code in MAC address does matter ?


Jean-Christophe Guillain wrote:
> I observed a strange networking behaviour of my Debian virtual host in
> function of the MAC address I use. It seems that when I use an existing
> constructor code, networking works without any problem, but is
> impossible in the other case...
> Ex. :
> - vif = [ 'mac=aa:00:00:00:00:55, bridge=xen-br0' ] -> no problem
> - vif = [ 'mac=df:00:00:00:00:55, bridge=xen-br0' ] -> the bridge does
> not transmit my packets apparently. No DHCP possible, and when I used a
> static address I can't ping the bridge from the guest...
> Is it normal ? Is it really related to constructor code ?
> I use a Xen 2.0.6 on a Debian Sarge host with kernels

Have you seen http://wiki.xensource.com/xenwiki/XenNetworking ?

Which says:

Whehn choosing MAC addresses to use, ensure you choose a unicast address. That 
is, one with the low bit of the first octet set to zero. For example, an 
address starting aa: is OK but ab: is not. It is best to keep to the range of 
addresses declared to be "locally assigned" (rather than allocated globally to 
hardware vendors). These have the second lowest bit zero in the first octet. 
For example, aa: is OK, a8: isn't.

In summary, an address of the following form should be OK:


where X is any hexadecimal digit, and Y is one of 2, 6, A or E.


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