Why doesn't "ifconfig" work on some of my machines?
Solution 1:
I think this is when ifconfig is in /usr/sbin which is not in a non-admin user's path. Try:
/sbin/ifconfigSolution 2:
Redhat-based distros don't include much in root's path for (imho, misguided) security reasons. Add /sbin;/usr/sbin;/usr/local/sbin to your path, or just memorise where your commands are stored are and specify the paths when running.