How to add a service IP to a ProxMox 3 cluster ?

Hi,

I'm making some tests with ProxMox 3 clustering.
I built a cluster with 3 nodes and created a shared GlusterFS volume as a shared storage which is working quite good.

Clustering is working well and I can administer the whole cluster from any node but I'd rather use a service IP that would be balanced by corosync so that I don't have to worry about a single node and access my cluster through this service IP.

How can I do that ?
How can I modify the cluster configuration so that I can add a service IP ?
Is it possible without arming any futur update process ?

Thanks for any help.

Regards.