On Thu, Jan 17, 2013 at 07:44:39PM +0100, Tobias Klausmann wrote:
> Hi! 
> 
> On Thu, 17 Jan 2013, Peter Stuge wrote:
> > Tobias Klausmann wrote:
> > > It has been rather nifty that if I walk up to a random machine
> > > with exactly one NIC (that I've been asked to examine/fix), I
> > > _know_ that there will be eth0 and only that.
> > 
> > Only as long as that system hasn't seen *another* NIC first, if it
> > has persistent interface name udev rules.
> 
> I was talking about strictly kernel order vs. predictable-net.
> Persistent-net has VM-related downsides as pointed out in the
> udev page about the whole thing.

The problem is the kernel names are not dependable.

If you have one network card right now, sure, it will be eth0.
But, suppose you buy another network card and plug it into the system.
Now you have no way to know that eth0 will refer to the card you think
it does.

With the predictable names, on my system for example, I know that enp1s5
will always refer to the same nic, even if I put a new one in the box.

William