howto determine network device unit number? device.hints?

[Yony Yossef]

> 
> you may not change unit numbers as they are strictly 
> controlled by kernel.
> However, on freebsd 5.3+, you may use 'ifconfig name <your-name-here>'
> to achieve the same affect
> 

Sorry, I don't understand the usage of ifconfig you suggested and the effect
it will cause.
Can you please explain it?
Yony

> 
> Yony Yossef wrote:
> > Hi,
> >
> > I would like to determine the unit number of my network cards, e.g.
> > make the device on pci0:16 be assigned every time with unit 
> number 0 
> > and pci0:19 with unit number 1.
> >
> > Is it done by /boot/device.hints?
> > if so, how?
> >
> > My cards are:
> >
> > mtnic0 at pci0:19:0:0:     class=0x020000 card=0x001715b3 
> chip=0x636815b3
> > rev=0xa0 hdr=0x00
> > mtnic1 at pci0:16:0:0:     class=0x020000 card=0x001715b3 
> chip=0x636815b3
> > rev=0xa0 hdr=0x00
> >
> > So I've tried:
> >
> > hint.mtnic.0.at="pci0:16"
> > hint.mtnic.1.at="pci0:19"
> >
> > but it doesn't work. They keep switching arbitrarily.
> > I'm using FreeBSD 7.0.
> >
> > Thanks
> > Yony