I understand how to change the ip address permanently however, I need to also make a permanent change to the subnet mask. How would I accomplish this.
Which OS?
Unix SYS V/68 R3V7
What platform are you on AIX / HPUX etc.?
Motorola VME computer
Try searching for a network config file under the /etc/init.d/ directory. You can grep for the subnet keyword in the files under that directory.
grep -i subnet /etc/init.d/*