When you install or start Adobe Experience Manager (AEM), there's a cluster-related startup failure in the logs.

For example: "javax.jcr.RepositoryException: Unable to register data store in cluster."

Solution

On dual-stack machines, make sure that your JVM is using the preferred protocol stack. For example, add the prefer IPv4 addresses [1] at the startup script.

[1]     -Djava.net.preferIPv4Stack=true