8.3. Interface Control Scripts

The interface control scripts activate and deactivated system interfaces. There are two primary interface control scripts, /sbin/ifdown and /sbin/ifup, that call on control scripts located in the /etc/sysconfig/network-scripts/ directory.
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

Warning

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 Section 8.4, “Network Function Files” for more 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:
  • ifup-aliases — Configures IP aliases from interface configuration files when more than one IP address is associated with an interface.
  • ifup-ippp and ifdown-ippp — Brings ISDN interfaces up and down.
  • ifup-ipsec and ifdown-ipsec — Brings IPsec interfaces up and down.
  • ifup-ipv6 and ifdown-ipv6 — Brings IPv6 interfaces up and down.
  • ifup-ipx — Brings up an IPX interface.
  • ifup-plip — Brings up a PLIP interface.
  • ifup-plusb — Brings up a USB interface for network connections.
  • ifup-post and ifdown-post — Contains commands to be executed after an interface is brought up or down.
  • ifup-ppp and ifdown-ppp — Brings a PPP interface up or down.
  • ifup-routes — Adds static routes for a device as its interface is brought up.
  • ifdown-sit and ifup-sit — Contains function calls related to bringing up and down an IPv6 tunnel within an IPv4 connection.
  • ifup-sl and ifdown-sl — Brings a SLIP interface up or down.
  • ifup-wireless — Brings up a wireless interface.

Warning

Removing or modifying any scripts in the /etc/sysconfig/network-scripts/ directory can cause interface connections to act irregularly or fail. Only advanced users should modify scripts related to a network interface.
The easiest way to manipulate all network scripts simultaneously is to use the /sbin/service command on the network service (/etc/rc.d/init.d/network), as illustrated the following command:
service network <action>
In this example, <action> can be either start, stop, or restart.
To view a list of configured devices and currently active network interfaces, use the following command:
service network status