Red Hat Bugzilla – Bug 314551
udev incorrectly renames a network interface
Last modified: 2009-12-14 15:41:37 EST
Description of problem:
I've 3 physical network interfaces (1 PCI NIC rtl8159 - eth0, 1 Onboard NIC e100
- eth1, and 1 USB NIC cdc-ether - eth2). All 3 physical interfaces work fine
(and initialized to their default names) when running default 'kernel'. In
'kernel-xen' (running as domain 0) at startup all NICs are initialized to their
default names, but when 'eth2' is disconnected and reconnected, it gets detected
as 'eth3', whereas 'eth2' used to be still present, but MAC address changed to
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Turn off the ADSL modem (to which eth2 is connected).
2. Turn on the ADSL modem, now eth3 will appear, but eth2's MAC address gets
changed to "00:00:00:00:00:00".
The 'eth2' interface now gets detected as 'eth3' whereas 'eth2' is still present.
'eth2' should be always detected as 'eth2'.
The 'dmesg' output is attached.
Created attachment 212711 [details]
Please provide output of
- 'ifconfig -a'
- 'brctl show'
Please capture the data both before and after unplugging & reconnecting the
Created attachment 221711 [details]
Output of commands before power-cycling modem
Created attachment 221721 [details]
Output of commands after power-cycling modem
Ok, so the problem is thus:
- When booting the kernel-xen, XenD will start (/etc/init.d/xend script)
- XenD by default attempts to place your primary active NIC into a bridge at
- You have 3 nics, eth0, eth1, and eth2. It looks like eth2 is the only active
NIC. Therefore XenD puts eth2 into a bridge
- When eth2 is enslaved, it gets renamed to peth2, and 'eth2' becomes the
- When you turn off the modem, the physical device, peth2, goes away. The
bridge, eth2, stays around.
- When you turn it back on, eth2 (the bridge) is still there, so your modem
The core issue here is that XenD's bridging setup assumes that your primary NIC
never goes away. There is no way to fix it work with dynamic devices which come
& go, so the best option is to turn it off, or ensure that another permanently
connected device is always active at boot.
To turn it off, edit /etc/xen/xend-config.sxp and find the line refering to
And change it to
This will ensure that your ADSL modem device, or any other device, is never
bridged by XenD at boot time.