can i completely delete and recreate my network interfaces?

[Robert P. J. Day]

On Sun, 13 Jan 2008, John Summerfield wrote:

> Robert P. J. Day wrote:
> >   let's see if i can make a long story short.  for the sake of sheer
> > experimentation, i wanted to see if i could *totally* remove all
> > networking configuration from a gateway laptop running F8 x86_64, then
> > use system-config-network (henceforth, s-c-n) to recreate it from
> > scratch.
> >
> >   the underlying hardware (from lspci):
> > ...
> > 02:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8036
> > PCI-E Fast Ethernet Controller (rev 10)
> > ...
> > 08:07.0 Network controller: Broadcom Corporation BCM4318 [AirForce One
> > 54g] 802.11g Wireless LAN Controller (rev 02)
> > ...
> >
> >   so i went into s-c-n, removed all traces of network configuration
> > under both the Devices and Hardware tabs, saved that, removed the
> > lines from /etc/modprobe.conf:
> >
> >   alias eth0 sky2          (um ... i think that's what it was)
> >   alias wlan0 b43	   (added previously by me for wireless)
> >
> > i then unloaded the above modules from the system, and verified that
> > the directory /etc/sysconfig/networking/devices is utterly empty.  so
> > ... should i be able to put stuff back?
> >
> >   if i invoke s-c-n again, i'm not surprised to see both the Devices
> > and Hardware tabs totally empty.  so how could i recreate the wired
> > interface eth0?  if i try to add a new device of type "Ethernet
> > Connection", i'm given only a choice of "Other Ethernet Card", and i
> > don't see a corresponding entry for that ethernet controller.  should
> > i?  or am i going about this the wrong way?  what would be the correct
> > recipe to restore my eth0 interface?
> >
> >   i have just as little success trying to restore the wlan0 wireless
> > interface, *until* i add the line
> >
> >   alias wlan0 b43
> >
> > back to /etc/modprobe.conf, at which point restoring the wireless
> > interface via s-c-n is a piece of cake (it even handles the access
> > point's WEP).
> >
> >   so wireless is back, but still no wired interface eth0, although i'm
> > puzzled that the directory /etc/sysconfig/networking/devices now
> > contains three files:
> >
> > ifcfg-eth0
> > ifcfg-wlan0
> > keys-wlan0
> >
> > and ifcfg-eth0 contains:
> >
> > # Intel Corporation PRO/100 VE Network Connection
> > DEVICE=eth0
> > BOOTPROTO=dhcp
> > HWADDR=00:E0:B8:BF:7C:3F
> > ONBOOT=yes
> > TYPE=Ethernet
> >
> >   so what have i messed up?  is there, in fact, any way to restore
> > eth0?  thanks.
>
> I think you need to reboot.

i've tried that.  as a test, i once again removed every trace of
networking (both wired and wireless) using s-c-n, then rebooted.  (i
removed wireless because i didn't want anything related to wireless to
get in the way of trying to restore eth0.)

now that i've rebooted, here's what i see.  "ifconfig" shows me only
the interface lo.  "ifconfig -a", on the other hand, also shows me
entries for eth0 and wlan0, but neither of them are UP nor do they
have assigned IP addresses.  (they both have MAC addresses so that's,
i guess, a good sign.)

and when i run s-c-n, the Devices tab is still empty, but the Hardware
tab shows *three* entries:

  Broadcom BCM4318 ...   | Ethernet | eth0  | ok
  Broadcom BCM4318 ...   | Wireless | wlan0 | system
  b43                    | Wireless | wlan0 | system

it's as if the wireless, seeing that eth0 is currently unused, just
grabs it for some reason.  that's why i tried to disable wireless
entirely before trying to restore eth0.

in addition, /etc/sysconfig/networking/devices is still entirely
empty, and /var/log/messages contains the boot-time lines:
...
... sky2 0000:02:00.0 v1.18 addr 0xd0200000 irq 18 Yukon-FE (0xb7) rev 1
... sky2 eth0: addr 00:03:25:35:4c:8f
...

and that MAC address does, in fact, match what i get from running
"ifconfig eth0".  so it's clear that the boot process sees the
ethernet device, it just doesn't do anything with it, and wireless
comes along and somehow takes control of it.  or something like that.

in short, after wiping all networking config info from the machine,
it's not hard to restore the wireless.  but i have yet to figure out
how to restore the wired and, worse, it seems restoring the wireless
first is going to get in the way of recreating eth0.

so i'm still at a bit of a loss as to how to get back my eth0.

rday
--


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Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

Home page:                                         http://crashcourse.ca
Fedora Cookbook:    http://crashcourse.ca/wiki/index.php/Fedora_Cookbook
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