Using device.hints to determine network device unit number

[Yehonatan Yossef]

Hi, 
 
I would like to determine the unit number of my network cards, make the
device on pci0:16 appear always as mtnic0 and pci0:9 appear always as
mtnic1.
 
# pciconf -l | grep mtnic
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
 
Is it done by /boot/device.hints?
if so, how? I've tried:
 
hint.mtnic.0.at="pci0:16"
hint.mtnic.1.at="pci0:19"
 
but it doesn't work. They keep switching upon reboot.
I'm using FreeBSD 7.0.
 
Thanks
Yony