Interface Control Scripts - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

Chapter 14. Network Interfaces
ifcfg-lo
A local loopback interface is often used in testing, as well as being used in a variety of applications
that require an IP address pointing back to the same system. Any data sent to the loopback device
is immediately returned to the host's network layer.
Warning
The loopback interface script, /etc/sysconfig/network-scripts/ifcfg-lo,
should never be edited manually. Doing so can prevent the system from operating
correctly.
ifcfg-irlan0
An infrared interface allows information between devices, such as a laptop and a printer, to flow
over an infrared link. This works in a similar way to an Ethernet device except that it commonly
occurs over a peer-to-peer connection.
ifcfg-plip0
A Parallel Line Interface Protocol (PLIP) connection works much the same way as an Ethernet
device, except that it utilizes a parallel port.
ifcfg-tr0
Token Ring topologies are not as common on Local Area Networks (LANs) as they once were,
having been eclipsed by Ethernet.

14.3. Interface Control Scripts

The interface control scripts activate and deactivated system interfaces. There are two primary
interface control scripts that call on control scripts located in the /etc/sysconfig/network-
scripts/ directory: /sbin/ifdown and /sbin/ifup.
The ifup and ifdown interface scripts are symbolic links to scripts in the /sbin/ directory. When
either of these scripts are called, they require the value of the interface to be specified, such as:
ifup eth0
Caution
The ifup and ifdown interface scripts are the only scripts that the user should use to
bring up and take down network interfaces.
The following scripts are described for reference purposes only.
Two files used to perform a variety of network initialization tasks during the process of bringing up
a network interface are /etc/rc.d/init.d/functions and /etc/sysconfig/network-
scripts/network-functions. Refer to
information.
After verifying that an interface has been specified and that the user executing the request is allowed
to control the interface, the correct script brings the interface up or down. The following are common
interface control scripts found within the /etc/sysconfig/network-scripts/ directory:
162
Section 14.5, "Network Function Files"
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