What do you want to failover? your state? ok, then, in a web application, the state is generally in the httpsession (or in a SFSB).
Consequently, if your http-session is replicated and you have an homogeneous deployement of your app in all nodes of the cluster, you don't need anything else: the servlet will always access the local EJB and never fail to another node (no need for this).
Is that clearer?