Red Hat Enterprise Linux makes use of several files that contain
important common functions used to bring interfaces up and down.
Rather than forcing each interface control file to contain these
functions, they are grouped together in a few files that are called
upon when necessary.
The /etc/sysconfig/network-scripts/network-functions
file contains the most commonly used IPv4 functions, which are
useful to many interface control scripts. These functions include
contacting running programs that have requested information about
changes in an interface's status, setting hostnames, finding a
gateway device, verifying whether or not if a particular device is
down, and adding a default route.
As the functions required for IPv6 interfaces are different than
IPv4 interfaces, a /etc/sysconfig/network-scripts/network-functions-ipv6
file exists specifically to hold this information. The functions in
this file configure and delete static IPv6 routes, create and
remove tunnels, add and remove IPv6 addresses to an interface, and
test for the existence of an IPv6 address on an interface.
