Linux – interface id for ethernet card

As mentioned by tzafrir.net without much more explanation, on Debian based systems which include Ubuntu you need to check the /etc/udev/rules.d/70-persistent-net.rules file and you will find a line similar to:

# PCI device 0x14e4:0x170c (b44)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:15:c5:6d:b1:9e", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

You will obviously find one for with NAME="eth0" and another with "NAME=eth1" but will each have the respective MAC addresses. You can simply swap the NAME values and restart your computer and the system will rename them. You could even name them something different like wan or lan it doesn't matter so long as your routes and other configurations use the same names.

On RedHat based systems, including Fedora and CentOS, this would be accomplished by changing the HWADDR line found in the appropriate /etc/sysconfig/network-scripts/ifcfg-ethX file.

The point of it is to maintain the same NIC upon reboots as the kernel has been known in the past to change the order that PCI cards are addressed which can swap the NIC order.

So, the 'devXXXXX' interface was generated whenever I plugged in the Apple USB Ethernet adapter (and went away when unplugged), but it changed, so I don't expect it to have the same device name after a reboot. (Not to mention I couldn't get an IP to stick to it when configuring using system-config-network-tui.)

When plugging the Apple USB Ethernet adapter in, I got the following in /var/log/messages:

Sep 21 13:40:15 hostname kernel: usb 1-6: new high speed USB device using ehci_hcd and address 6
Sep 21 13:40:15 hostname kernel: usb 1-6: configuration #1 chosen from 1 choice
Sep 21 13:40:15 hostname kernel: ASIX USB Ethernet Adapter:v4.1.0 17:04:38 Sep 20 2011
Sep 21 13:40:15 hostname kernel:     http://www.asix.com.tw
Sep 21 13:40:15 hostname kernel: eth%d: status ep1in, 8 bytes period 11
Sep 21 13:40:15 hostname kernel: eth1: register 'asix' at usb-0000:00:1d.7-6, ASIX AX88772A USB 2.0 Ethernet, ffff8100769819a8M

I did find a line reading alias eth1 skge in /etc/modprobe.conf (for that odd eth1 interface that is not anything and never shows up as connected) and commented it out (esp. since /var/logs/messages show the log registering asix as eth1). After doing so, giving eth1 a static IP using system-config-network-tui, and disconnected & reconnecting the Apple USB Ethernet adapter, it now always shows up as eth1 and with the correct ethernet address. I can also ping hosts on that subnet, so this is working.

The main issue appears to have been the conflict between the hard-coded alias and the asix module trying to register as the same name.

One additional note: It seems to change the default route to the Apple USB Ethernet adapter whenever it's plugged in, so you have to be sure to check that & adjust, if necessary.