howto determine network device unit number? device.hints?

[Yony Yossef]

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