From Fedora Project Wiki

Dualstack Networking


IPv4 and IPv6 host/service name resolution doesn't work very well in Fedora. The getaddrinfo() function in glibc returns wrong results in many cases. This feature aims to fix a bunch of name resolution bugs in glibc that prevent applications from fully using name resolution functions without doing a bunch of workaround.


Current status

  • Targeted release: Fedora 19
  • Last updated: 2013-01-08
  • Percentage of completion: 5%

Detailed description

Fedora supports dualstack global networking. That means the computer with Fedora is connected to internet using both IPv4 and IPv6 protocols. But many important system services and applications either don't do IPv6, do it incorrectly, or don't cope with various network conditions.

Unfortunately, while trying to improve IPv6 support, some IPv4 use cases became broken as well. That's why the goal of this feature is not only to support IPv4, but to support all possible real-world cases.

Dualstack-ready software must cope with all possible scenarios including IPv4-only connectivity, IPv6-only connectivity and dual connectivity. The software must also cope with node-local (aka localhost) networking, which as been used by software for decades.

Though it would be nice to have all applications in Fedora fixed to work in any of the scenarios, it is not feasible to test that. Therefore this feature is about major software used in servers, desktops and laptops. The list of such applications will be completed over the time.

Bugs related to dualstack networking should be added to the following tracker bug:

Also see:

Benefit to Fedora

One of Fedora's goals is to be a modern linux distribution that will work in modern environments. For this to be achieved, proper IPv4-only support and proper dualstack support is a MUST. IPv6-only use cases are rare but may become more common at any time. It's better to be prepared for those, too.


Application software used on day-to-day basis should be correctly handling IPv4-only, IPv6-only and dualstack use cases.


  • glibc: name resolution must work properly
  • glib: provides networking API for applications

System services:

  • knfsd


Note: Network configuration tools are out of scope of this feature. Network testing tools were moved to a separate feature page. See Networking#Fedora_feature_pages for other network-related features.

How to test

This is the most difficult part. We are going to combine the following approaches to testing:

  • Everyday use of Fedora in various network environments
  • Testing the tracked bug reports
  • Specific tests, e.g. for getaddrinfo() and glib API

User experience

Users currently experience networking problems in various environments even during the most basic use of their system because of principal problems in the distribution. These problems would go away.


Not known.

Contingency plan

This feature is about fixing all important parts of the distribution. We do not expect the required changes to negatively affect the rest of the packages. But if any problems occur, we are ready to help fixing them before the respective version is released. As a last resort, any problematic change can be reverted.


Release notes

Dualstack networking is fully supported and glibc and other packages will be tested for not including fundamental design flaws and important bugs regarding IPv4 and IPv6 support.

Comments and discussions

See Talk:Features/DualstackNetworking