[CentOS] Strange XEN on CentOS HWaddr Address Issue

Mathew S. McCarrell mccarrms at gmail.com
Tue Aug 4 17:57:11 UTC 2009


I think the following link answers your question about the MAC changes.  You
may find more useful links on the resources page of the Running Xen site


If you performed a fresh install without Xen, you would notice that it has
not permanently modified the MAC address of your system.

Hope that helps.


Mathew S. McCarrell
Clarkson University '10

mccarrms at gmail.com
mccarrms at clarkson.edu

On Tue, Aug 4, 2009 at 1:30 PM, Brett Serkez <bserkez at gmail.com> wrote:

> > Maybe because you are looking at the bridge's mac and not the
> > ethernet's which would be peth0.
> No I am not.  dmesg shows the kernel messages at boot and it is
> looking at the physical device, let's not get distracted, the issue is
> clear in this regard.  As I previously stated, this happens even when
> uninstalling XEN and booting off the non-XEN kernel since the install
> of XEN.
> > indeed, AFAIK all hardware adapters start with 00. This must have been
> set
> > in the BIOS or with a boot option or in the network config.
> This was helpful, gave me places/incentive to continue looking.
> In /etc/sysconfig/network-scripts/ifcfg-eth1 I found:
> # Realtek Semiconductor Co., Ltd. RTL-8169 Gigabit Ethernet
> DEVICE=eth1
> HWADDR=00:40:F4:CE:E6:7B
> So now I know what the original MAC address was.
> Here is where it gets interesting.  The following file was modified at
> the date/time that the XEN kernel was first booted:
> /etc/sysconfig/hwconf
> and it has fe:ff:ff:ff:ff:ff  for BOTH network adapters:
> desc: "Realtek Semiconductor Co., Ltd. RTL-8169 Gigabit Ethernet"
> networfe:ffddr: fe:ff:ff:ff:ff:ff
> vendorId: 10ec
> deviceId: 8169
> subVendorId: 10ec
> subDeviceId: 8169
> pciType: 10
> desc: "Intel Corporation 82562EZ 10/100 Ethernet Controller"
> network.hwaddr: fe:ff:ff:ff:ff:ff
> vendorId: 8086
> deviceId: 1050
> subVendorId: 8086
> subDeviceId: 303a
> Everything I'm finding is re-enforcing my original theory that XEN
> modified the hwaddr of this NIC.
> The question continues to be what caused this and how to change it
> back.  Given this is a stock system, I have to believe others must
> have/may run into this issue.
> Brett
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