Re: Depending on 2.4

[kimo_sabe@atdot.org]

On Thu, Feb 01, 2001 at 05:08:22PM -0600, Gordon Sadler wrote:
> On Thu, Feb 01, 2001 at 02:54:34PM +0000, Patrick Caulfield wrote:
> > I'm currently packaging the DECnet progs and they are dependant on a 2.4 kernel,
> > is there any recommended way to enforce this or should I just put a check in the
> > startup script and a note in the description?
> > 
> > Another thing it does is to change the MAC address of any/all ethernet cards in
> > the system (requiring a reboot). I've put a bit fat warning (debconf: critical)
> > in the package, should this be enough or should I have a flare go up from the
> > back of the machine too ;-)
> > 
> Hmm, the MAC address of most (all?) NIC's is burned into the ROMs on
> the cards. Ensuring they are globally unique, registered with ...( hmm,
> cannot remember organization's name).
  Almost, it's burned into rom(or more often, written to flash) so that the
card will have a persistant, and hopefully unique id. If you take a look
most(all?) NIC drivers in the kernel you'll see they read the MAC address
from the card and place it in a structure.  That structure is used when
constructing packets to, among other things, provide the source MAC address.
  The ethernet frames are generated completely in software, so unless the
NIC transparently mangles all outgoing frames, the MAC address isn't tied to
the hardware.
  And no, you don't need to reboot to change MAC addresses.  When I was
living in the dorms I'd occationally change ethernet cards for whatever
reason.  Instead of going to another computer to update my MAC in the DHCP
database(and waiting for it to take effect), I'd just manually set the MAC
of the old card. DHCP would give me my IP, and I'd update the record for the
next time. Easy.

  - Nick Lopez
    kimo_sabe@atdot.org
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