Mac address changes upon reboot on PE2950

Hanne Munkholm hanne at
Wed Feb 2 03:10:15 CST 2011

On Tue, 1 Feb 2011, Robert von Bismarck wrote:

> Hello,
> We had an issue this morning, where one of our servers (PowerEdge 2950
> GenII) changed the mac address of it's on-board NICs to something
> different during or after a reboot.
> The server was updated using 'yum update' from CentOS 5.3 to CentOS 5.5
> (x86_64) and was then rebooted. After that the mac addresses were
> changed.


> So I'm asking if anyone has seen this behavior before, as I can't point
> out if this is a Dell issue, a Linux issue, a CentOS issue, or just
> plain old magic ?

It is a udev thing and it is not specific for CentOS. It also
happens when you upgrade Debian - I saw it for the first time a
couple of years ago.

In Debian you can hardwire the Mac address to the ethernet
interface name in /etc/udev/rules.d/70-persistent-net.rules.

In RedHat/CentOS I don't know but it sounds likely that setting
the HWADDR= in /etc/sysconfig/network-scripts/ifcfg-ethX, as
someone suggests, will do the trick.

Med venlig hilsen / Best regards
Hanne Munkholm                      Email: hanne at
Systemadministrator                 Tlf: +45 35 32 13 49

Københavns Biocenter, Biologisk Institut
Ole Maaløes Vej 5, 2200 København N

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