You will need a load-balancer (hw or sw).
Let me see if understand this correctly, so it is NOT possible to have just JBoss clustering running but I must have load-balancer to work in conjunction with the JBoss clustering?
What are you trying to achieve with your cluster? Clustering will work without a load balancer but you won't have server load balancing or session failover. The nodes will still be in a cluster and some cluster functionality will work (e.g., HA-JNDI, DistributedState, TreeCache replication etc.).