cluster and domain are two different concepts.
domain - is administrative and share the configuration and deployments in server-groups. You are able to manage/monitor similar servers with a domain
cluster - is at application level, i.e. EJB's are loadbalanced, there is a failover for web sessions or stateful ejb's
So you can use a domain configuration to simplify your management.
For the cluster you need to start the server with an *ha* profile in standalone or domain mode, and ensure that you use the same JGroups configuration to be clustered.
You should see a message how many cluster members the server see.
The documentation can be found here Documentation - JBoss AS 7.1
But I recommend to start with WildFly (successor or AS7) or EAP6 because the AS7.1.1 is quite old
Thanks for your advises/information. Will try to set-up the installation as per the link provided.Will get back with details soon.
Should be simple
Let me know if you have problems or questions.