IPv6 needed by Windows for Failover Clustering / SQL AlwaysOn?

OS Win 2012 / SQL 2012

I'm trying to determine if IPv6 is needed, and within what capacity (traffic-wise, OS enabled-wise, etc.) to support Windows Failover Clustering for SQL AlwaysOn Availability Groups.

A proposal from a colleague is that it is, and they are referencing this article.


I do not gather from this article that IPv6 is needed, whether in the OS level or on the Core/Router traffic, for it to work.

But I did want to check in case I misunderstand what is needed, or how best to approach.

I don't want to open up IPv6 on all servers, or have networking have to open up IPv6 on the firewalls, if it's unnecessary.

Any advice/experience/input here appreciated.
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lcohanDatabase AnalystCommented:
"The majority of the internal testing for Failover Clustering is done with IPv6 enabled. Therefore, having IPv6 enabled will result in the safest configuration for your production deployment."

So I would use it instead of disabling it in particular you mention SQL 2012 "SQL AlwaysOn Availability Groups" requirement.


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garryshapeAuthor Commented:
Does that mean just enabling IPv6 on the servers? Or also having to open up IPv6 traffic on the core routers?
I can't tell sometimes if the feature just needs to be enabled due to finicky OS/Application configurations, or if indeed all  IPv6 network traffic needs to be permitted within the environment, and for all systems or just those unique to the cluster
lcohanDatabase AnalystCommented:
I'm pretty sure is just between the nodes and for the sole purpose of clustering alone. IPv4 will be used for regular "user" traffic against the SQL cluster.

From same link above "If both IPv4 and IPv6 are enabled (which is the default configuration), IPv6 will be always used by clustering. The key take away is that it is not required to configure IPv4 when the IPv6 stack is enabled and you can go as far as to unbind IPv4. Additionally, you can use link-local (fe80) IPv6 address for your internal cluster traffic so IPv6 can be used for clustering even if you don’t use IPv6 for your public facing interfaces."
garryshapeAuthor Commented:
So should just probably have to check IPv6 on the servers but not unblock IPv6 traffic on the router
lcohanDatabase AnalystCommented:
That is correct - the nodes of the cluster will "talk" on IPv6 and external traffic in classic IPv4
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