How to set tcp/ip info each boot time?

Each time when I boot my qnx6.1,I must config my tcp/ip info. And I will
/etc/net.cfg file has changed after I config.
But when I reboot qnx,I will see the file/etc/net.cfg is the same as I
config before,so I have to config again.
Can anyone tell me what had happened and tell me the right method to set
tcp/ip info?
Thanks a lot.