When configuring Universal Messaging for clustering, it is not essential but it is often recommended to have a dedicated interface for cluster communications. Replication of data, state and other cluster negotiation traffic is very high priority so we need to ensure that it is not delayed in any avoidable way. If the cluster cannot form, then no client traffic will be able to flow, so it is vital that the client traffic cannot impact the cluster formation. If you have lots of clients constantly trying to access the server and getting disconnected because the cluster isn't formed, they will be competing to connect at the same time as nodes within the cluster are trying to connect to one another.

In order to have dedicated cluster communications you need to create a new interface on each node within the cluster. On this new interface you need to select the basic tab and uncheck the checkbox for Allow client connections before clicking Apply. Your clients will now only be able to connect to the original interface whereas the cluster nodes can communicate on both. Cluster nodes will automatically send information about this new interface to one another over the existing connection, so from now on they will be able to use either if they disconnect from each other.

Please note that modifying the interface will cause it to stop and be restarted, so all connections on that interface will be dropped when you click Apply.