Re: Specifying names for tap interfaces

[Scott Solmonson <scosol%scosol.org@localhost>]

This has been a pain point for me before-

Since MACs are UUIDs-
Is there a good reason why any interface "naming" (essentially,
aliasing) should be automated at all?
(specifically to avoid and card removal/replacement/moving problems)
Is there any reason why, in the system/OS-level config, a fully manual
mapping of MAC1->eth0, MAC2->eth1, MAC(n)->eth(n) shouldn't be
*required*?
It's difficult for me to find one.

If I replace a NIC with another, and the automation swaps its naming
with another NIC, my firewall is now broken, potentially in a VERY
BAD(TM) way. If I'm adding more NICs and move an existing one to a
different slot, and the automation changes up its naming based upon
seeing the same MAC in a different slot (and/or gets entirely
confused, which has happened to me in Linuxland), that's VERY
ANNOYING(TM).

I'm eager to hear any and all arguments in support of automated NIC
naming, versus a one-time static-mapping config similar to that which
is needed to simply assign an IP address and netmask etc :)

-SS
--
NUNQUAM NON PARATUS ☤ INCITATUS ÆTERNUS


On Sun, Jun 24, 2012 at 12:14 PM, Gert Doering <gert%greenie.muc.de@localhost> 
wrote:
> Hi,
>
> On Sat, Jun 23, 2012 at 04:09:06PM +0200, Manuel Bouyer wrote:
>> > Linux's method associates names by driver type (eth0, eth1, etc).
>>
>> Yes, and it's also associated with the hardware. On a system with a
>> add-on PCI ethernet called eth0, if you remplace it by another PCI ethernet
>> (even if it's the same model, as the name is actually attached to the
>> ethernet address) it'll be called eth1. You have to edit sysconfig files
>> to have it named eth0 again.
>
> That's udev, and it's considered a feature that the system remembers
> the MAC address of ethernet cards, so if you have a system with multiple
> ethernet cards and change "something in the hardware" (like: remove
> card #1) the ethX numbers do not change.
>
> Of course things break if you replace a card and do not update the
> (userland) rule file that maps "mac address $foo to eth$bar".
>
> Not perfect either, but done with a reason - and since it's all userland,
> can be adjusted to whatever makes sense.  I think you could even have
> Linux name all Intel Pro/100 cards fxp0, fxp1, fxp2, ... :-)
>
> gert
>
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> Gert Doering - Munich, Germany                             
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