What is the IPV4_FAILURE_FATAL ifcfg directive and under what scenarios would I want to use it?

Question

CentOS / RHEL 6

I recently learned that there's a ifcfg directive called IPV4_FAILURE_FATAL exists for use in the files located here: /etc/sysconfig/networking-scripts/ifcfg-*. But I'm having a difficult time finding information about it.

• What does it do?
• Under what circumstances would I ever want it set to "yes"?

Solution

From the Fedora Project's wiki page on Anaconda Networking:

If both IPv4 and IPv6 configuration is enabled, failing IPv4 configuration of activated device means that activation is considered as failing overall (which corresponds to Require IPv4 addressing for this connection to complete checked in nm-c-e or IPV4_FAILURE_FATAL=yes in ifcfg file).

Putting it another way it's saying that if a connection is setup for both IPv4 and IPv6, with this option set to yes, the setup of the said connection will be reported as failed, even if IPv6 is setup, and IPv4 is not.