I hava a Slackware 10.1 with 2 network interfaces, both interfaces are the same model VIA RHINE so they use the same module. The computer belongs to a NIS network so if the network card is down the computer will not log on, because of that I have to choose a specific order for the network cards going up, for that I made the folling steps:

1- I created a file called "mactab" at /etc with the content:
eth0 00:11:2F9:92:68 # MAC address of the card that I want to be the eth0
eth1 00:08:54:0C:71:72 # MAC address of the card that I want to be the eth1

2- At the end of the file /etc/rc.d/rc.inet1 I put the lines:
###############
# ETH REORDER #
###############
if [ -f /etc/mactab ]; then
/sbin/nameif -s
fi

I made this according to a manual found at the net, but when I restart or power on the computaer the network cards starts inverted and the computer doesn´t log in. Any clue?

This might be your problem. Its from the nameif manpage:

If you put your addition at the end of rc.inet1, then the network would already be up by the time the script gets to your addition.

What happens if you put your bit before the network interfaces are brought up?

I put my bit before the network interfaces are brought up but anything happened and after I brought down the eth0 and run the command nameif -s and started the eth0 interface but the same thing happened again..... Is there any other way to reorder the network interfaces?

ifrename??