[Gllug] Laptop Fedora MAC Address

[damion.yates at gmail.com]

On Thu, 12 Apr 2012, James Courtier-Dutton wrote:

> On 11 April 2012 18:41, Mick Farmer <mick at plan7.co.uk> wrote:
> > Dear GLLUGers,
> >
> > I'm running Fedora 16 on a Dell Inspiron laptop.
> >
> > When I boot the machine I get a Ethernet different MAC address!
> >
> > I can't imagine the laptop doing this (?), so is it a function of
> > Fedora?  If so, how do I stop it?
> 
> It is possible for software to change it.  If there is a bug in the
> ethernet driver or a corrupted eeprom, it might try to behave
> differently.

I've seen this myself although that was 5+ years ago on a debian system.

I think it was an issue with the ethernet driver.  It knew the
manufacturer value (1st three bytes?) but would randomly set the last
part of the MAC.
 
> Which hardware is the nic card?

I can't remember, but this was specific to that particular chipset when
I checked other servers.
 
> If you wish to fix it to a particular address, you can use the
> "ifconfig" to set it to a fixed value in one of the network init
> scripts.

I'm afraid my recollection of this is sketchy as this was years back and
once I resolved it I moved on.  If somebody from The Positive Internet
Company Ltd is skimming this thread, I documented this issue and the fix
in the server logs for whichever machine I first found it.  So an IMAP
search for messages from damion in the serverlogs archive might get the
details back.

My rough recollection of the issue goes like this:

- Box with upgraded OS worked 1st time but failed to join the network on
  subsequent boots.

- Raritan NetKVM attached by our suite gnome let me see that rather than
  getting an eth0 at boot, it had an eth1 and on a reboot an eth2 etc.

- The incrementing interface name explained why the network scripts at
  boot time were failing to assign correct details.  I started to track
  down the reason after seeing tmp files parsed in /var/<something>
  which were written by something in /etc/hotplug.d/ deciding that this
  machine was having new/different ethernet cards added between each
  boot.

- I eventually realised the MAC was changing!  I initially assumed this
  was an iffy driver, potentially a less capable OSS version of one with
  a binary blob that wasn't sandal-wearing/treehugging/"F"ree enough for
  the debian ranters^Wmaintainers, but then found it was doing this MAC
  changing mess even on the older dist release, however that
  lacked/cared about the hotplug side of stuff and so changing MAC
  addresses didn't bother it.

- I think I saw mention in the src/via Google, an inability to correctly determine
  the correct address meant it picked the last 3 bytes.  I can't
  remember if I fixed this with a parameter* passed to the
  insmod/modprobe via the correct module aliases configuration mechanism
  for this dist, or fudged the hotplug stuff to not increment the
  interface even if it did see a new MAC.

*I believe the BIOS was able to correctly see a single correct MAC.

Sorry if this is a bit jumbled/verbose.  It was a long time back, but as
I saw people suggest the OP was confusing IP with MAC I felt I should
jump in to say this is a real thing that can happen.

 - Damion
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