Network Setup in Linux

In Redhat and CentOS
Network interface cards are auto-discovered, they can be seen here; /etc/udev/rules.d/ in the file 70-persistent-net.rules

View the File:
cat /etc/udev/rules.d/70-persistent-net.rules

Output:
# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.

# net device () (custom name provided by external tool)
SUBSYSTEM==”net”, ACTION==”add”, DRIVERS==”?*”, ATTR{address}==”00:15:5d:xx:xx:xx”, ATTR{type}==”1″, KERNEL==”eth*”, NAME=”eth1″

# net device () (custom name provided by external tool)
SUBSYSTEM==”net”, ACTION==”add”, DRIVERS==”?*”, ATTR{address}==”00:15:5d:xx:xx:xx”, ATTR{type}==”1″, KERNEL==”eth*”, NAME=”eth0″

Note: In Linux 2.6 and above UDEV is the auto-discovery device manager and replaces the functionality of both hotplug and hwdetect. See: udev-ArchWiki and udev-Wikipedia
The network configuration files may also be auto created here: /etc/sysconfig/network-scripts/ in the file ifcfg-ethXX