Two NICs - swapped initialization

[Craig White]

On Wed, 2006-12-06 at 20:12 -0700, Darrin Chandler wrote:
> On Wed, Dec 06, 2006 at 06:03:07PM -0800, Kenneth wrote:
> > > The order of the naming of the devices is based on the order they are 
> > > discovered on the PCI bus.  It is possible that an update to the kernel 
> > > resulted in a reversal of the discovery order and so reverse the names. 
> > >   Back when I had a small linux router (P166 box) I had put entries in 
> > > modprobe.conf or conf.modprobe (been so long) that dictated the naming 
> > > of each device based on the MAC address to correct for this issue. 
> > > Another way might be to specify which NIC is which in the config files.
> > > 
> > > This is a RH specific link, but might help you figure out how to do 
> > > things in Gentoo.
> > > http://linux.dell.com/files/whitepapers/nic-enum-whitepaper-v2.pdf
> > 
> > Thanks for the link.  I guess I knew it had to be whatever the kernel scanned
> > first, I guess I was hoping there was a simple way to force it.  There was a
> > kernel update, and that was probably when the switch occurred.  I didn't use
> > the new one right away so I'm not sure.
> 
> This is probably the case. New kernel, that is. It used to be a much
> worse problem, as if you throw out probes some devices may not respond
> in the same timeframe always, so one boot you'd get one order, and the
> next boot you'd get a different order. Newer kernels are better about
> this, but it can still happen, IIRC. Not such a big deal for a desktop
> machine, but it's probably worth dinking with the config for a
> router/firewall.
----
this has been an issue when upgrading servers with multiple NIC's from
2.4 kernel to 2.6 kernel, since it almost seems that the reverse order
always happens which means a lot of tinkering in dense racks...not the
sport one engages in for fun. Dell wrote this about Red Hat because for
a fairly long time, that is all Dell supported but they now support SuSE
and limited support for Debian. It's been discussed several times on
linux-poweredge list (Dell).

One would think that an upgrade from one 2.6 kernel to another shouldn't
impact this though.

Craig