How to configure Clustered openfire server with only server and restrict other servers?

Am trying to create openfire clustered environment. I am testing with 4 different servers. When i enable clustering in all 4 with hazelcast, All 4 are automatically connected. How do i avoid the unwanted clustering in other word, How do i restrict my clustered servers only for 2 or 3? Please suggest.

And how can i restrict my servers to use only restricted ports, It starts from 5701 and try and checks different port by auto increment port numbers.Thanks in advance.