Wednesday, August 19, 2009

Mac address changed by itself (Debian linux)

Upon a hardware upgrade (new motherboard), the dual LAN card (Intel PRO100 S) installed on the system changed mac address by itself for one of its two adapters. The old harware mac 00:19:d1:25:d4:0b changed to 00:19:d1:55:7c:7c. Only the serial number changed and not the Vendor. I'm still looking for an explanation...

Here is the story (Debian Lenny)

The problem:
DHCP won't start (dhcpd will give IPs to only eth0). ifconfig shows eth0_rename, but no eth0 (like I used to have). Also, internal lan with a static IP address on eth0 won't work. It just won't start. This is how my /etc/network/interfaces looks like:
# Local - static IP
auto eth0
iface eth0 inet static

The solution:
As I understand, udev saw the new mac and changed the name from eth0 to eth0_rename. Why it did so, and not renamed it with eth1 or eth2 etc.... like it would suppose to do, I don't know - but that's another story. My best friend Google sent me to some pages about bugs related to udev (which probably is the culprit in this case). I found out that I should try to remove the file /etc/udev/rules.d/70-persistent-net.rules (as I understand, it is generated by udev upon installation/first reboot, then updated as new LAN hardware is added). Then reboot. My effort was rewarded with a brand new /etc/udev/rules.d/70-persistent-net.rules file and all the problems fixed. Of course, the new mac is there and the old one is gone...

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Updated / Actualizat: 2009-08-19.


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