why the net config can't be applied?

on my targetboard I have two net card,the chipset of one card is inter82559,the other is DEC21143,when system boots,first I use "io-net -d speedo -d tulip -ptcpip&"to drive them,and then I use “netmanager -r -f /etc/net.cfg” to make the netconfig valid,but it can’t,for I use “phlip” to open netconfig dialog and found the content of net.cfg is empty,but it’s very strange that if I change the setting in dialog and click “apply” button and exit the net can work correctly,but if I restart system and reopen the “phlip” dialog and the content of netconfig is empty again.

when I use “ifconfig en0” in my build file to set the en0,system say “address family not supported by protocol family”,who can help me?