[CentOS] Strange XEN on CentOS HWaddr Address Issue

Ross Walker rswwalker at gmail.com
Tue Aug 4 16:57:55 UTC 2009

On Aug 4, 2009, at 12:50 PM, Ross Walker <rswwalker at gmail.com> wrote:

> On Tue, Aug 4, 2009 at 12:30 PM, Brett Serkez<bserkez at gmail.com>  
> wrote:
>> On Tue, Aug 4, 2009 at 9:09 AM, Christoph Maser<cmr at financial.com>  
>> wrote:
>> <snip>
>>> When Xen starts does some trickery with your interfaces. You  
>>> should see
>>> FE:FF:FF:FF:FF:FF on device peth0 and the real MAC-address on device
>>> eth0.
>>> All Xen vif devices will show also MAC FE:FF:FF:FF:FF:FF. That is
>>> totally normal.
>> I  wanted to clarify on this point.  Understood as far as the above,
>> but the issue is that the PHYSICAL MAC was changed to
>>  This went so far as to still have this value even after rebooting on
>> the standard kernel and then uninstalling XEN:
>> # dmesg | grep eth1
>> eth1: RTL8110s at 0xee156c00, fe:ff:ff:ff:ff:ff, XID 04000000 IRQ 22
>> What ever happened during the first boot of XEN caused a permanent
>> change to this NIC as far as I can tell.
> Maybe because you are looking at the bridge's mac and not the
> ethernet's which would be peth0.

Actually that would be peth1

For a Xen server I find it better to disable the Xen network scripts  
and setup a static bridged or routed setup.

Then it is predictable and iptables is infinitely easier to setup.


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