Interface Control Scripts

The interface control scripts activate and deactivate 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 two interface control scripts are ifdown and ifup and are symbolic links to scripts in the /sbin/ directory. When either of these scripts is called, they require a value of the interface to be specified, such as:

ifup eth0 Determining IP information for eth0... done.

At that point, the /etc/rc.d/init.d/functions and /etc/sysconfig/network-scripts/network-functions files are used to perform a variety of tasks. See the “Network Functions” section of this chapter 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 for the type of interface device brings the interface up or down. The following interface control scripts are the most common:

• ifup-aliases — Configures IP aliases from interface configuration files when more than one IP address is associated with an interface.

• ifdown-cipcb and ifup-cipcb — Used to bring Crypto IP Encapsulation (CIPE) connections up and down.

• ifdown-ipv6 and ifup-ipv6 — Contains IPv6-related function calls using environment variables in various interface configuration files and /etc/sysconfig/network.

• ifup-ipx — Used to bring up an IPX interface.

• ifup-plip — Used to bring up a PLIP interface.

• ifup-plusb — Used to bring up a USB interface for network connections.

• ifdown-post and ifup-post — Contains commands to be executed after an interface is brought up or down.

• ifdown-ppp and ifup-ppp — Used to bring 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.

• ifdown-sl and ifup-sl — Used to bring a SLIP interface up or down.

Be aware that removing or modifying any scripts in the /etc/sysconfig/network-scripts/ directory can cause interface connections to act strangely or fail. Only advanced users should modify scripts related to a network interface.

You can also use the init script /etc/rc.d/init.d/network to activate and deactivate all network interfaces configured to start at boot time with the command:

/sbin/service network action 

where action is either start, stop, or restart. You can also use the command /sbin/service/network status to view a list of configured devices and currently active devices.