interface naming (eth[x], wlan[x], etc)

Hello,

I have a few questions that I'm hoping I can get answered. I'll number
them for easier reference in potential replies.

1) Is interface naming controlled by the kernel, i.e. does the kernel
assign names to devices as it detects them? Although eth0, eth1, etc,
are often used in /etc/network/interfaces, this is not what creates the
interfaces, correct? This only refers to specific interfaces (eth0,
eth1, etc) if they have been created by the kernel, right?

2) What about order? If you have multiple NICs in your system, are you
garanteed that they will always be detected in the same order?

3) Also, in most of the wireless HOWTOs I've come across, it is often
assumed that the wireless interface will be wlan0. However, on my linux
distro (ubuntu 6) I'm using ndiswrapper with a broadcom native win
driver (don't know if this has anything to do with it), and the
wireless interface is always eth1. However if I examine
/var/log/messages, I see diagnostic messages referencing wlan0.

Thank you,
spip

(E-Mail Removed) wrote:
> Hello,
>
> I have a few questions that I'm hoping I can get answered. I'll number
> them for easier reference in potential replies.
>
> 1) Is interface naming controlled by the kernel, i.e. does the kernel
> assign names to devices as it detects them? Although eth0, eth1, etc,
> are often used in /etc/network/interfaces, this is not what creates the
> interfaces, correct? This only refers to specific interfaces (eth0,
> eth1, etc) if they have been created by the kernel, right?
>
> 2) What about order? If you have multiple NICs in your system, are you
> garanteed that they will always be detected in the same order?
>
> 3) Also, in most of the wireless HOWTOs I've come across, it is often
> assumed that the wireless interface will be wlan0. However, on my linux
> distro (ubuntu 6) I'm using ndiswrapper with a broadcom native win
> driver (don't know if this has anything to do with it), and the
> wireless interface is always eth1. However if I examine
> /var/log/messages, I see diagnostic messages referencing wlan0.
>
> Thank you,
> spip
>


Hi,

I've been monitoring your message,because I am interested in these
subjects, too. Since nobody else answers, here is what I can tell you:

Subject 1: I don't know. I suspect that the "eth" prefix is related to
the hardware class of the network device (ethernet). The lowest-level
tool that I know is "/usr/sbin/ip". You can use it to list your devices
like this: "ip link show". More info available at http://lartc.org/howto/

Subject 2: The order depends on the scanning order of the PCI bus (or
whatever bus the network device is attached to). If you change your
kernel for example or if you have a detachable PCMCIA card (like me),
the scanning order might be different. In Debian you can fix the names
using the "mapping" stanza of /etc/network/interfaces. Do a "man
interfaces" to find out more. Or look at my configuration file - I use
the MAC address of the network cards:

################################################## #######
auto lo
iface lo inet loopback

auto eth0
mapping eth0 eth1
script /etc/network/scripts/get-mac-address.sh
map 00:30:B4:00:00:00 wifi
map 00:09:5B:E6:44:17 wifi
map 00:0A:E4:48:B0:85 fixed

iface wifi inet dhcp
wireless-essid MYSSID
wireless-channel 6
wireless-key restricted XXX-my-wep-key-XXX

iface fixed inet dhcp
################################################## ###

Subject 3: Sorry, I don't know.

Hope this helps,
Mihai