ifconfig: command not found

Both Fedora and RedHat identify NICs that are embedded on the motherboard by emN instead of ethN.

EDIT: If you want to prevent uvdev from renaming eth0 to em1 check this:

http://comments.gmane.org/gmane.linux.redhat.fedora.general/421412

ifconfig on Red Hat-esque boxes often lives in /sbin, which often isn't in the default path; try /sbin/ifconfig and see what you get.

The manual page for ip is a good place to start finding out about its options, behavior, output, &c.

By default, ifconfig wont be there in RHEL.

sudo yum install net-tools

will instal ifconfig in /usr/sbin/ifconfig