Thank you all for prompt replies and extra thanks to @Ancil McBarnett your answer was toward the right direction. I enabled all traffic in my security group (for testing purposes) as opposed to only tcp traffic before. As seen in the above logs the right port for ambari-server is 8440. That resolved the issue and now agents can be registered through Ambari. Just in sake of completeness my setup is: OS: RHEL-7.2 Ambari: 2.1.2 JDK: 1.8 Python: 2.7 ... View more