Solaris Cluster private network address problem

Hi,
I encountered problem on configuring private network address during initial cluster installation.
The network address provided as below:

Node 1
heartbeat 1 : 172.20.201.153
heartbeat 2 : 172.20.201.161

Node 2
heartbeat 1 : 172.20.201.154
heartbeat 2 : 172.20.201.162

When I try to enter the heartbeat address, it show messages as below:

  >>> Network Address for the Cluster Transport <<<

    The cluster transport uses a default network address of 172.16.0.0. If
    this IP address is already in use elsewhere within your enterprise,
    specify another address from the range of recommended private
    addresses (see RFC 1918 for details).

    The default netmask is 255.255.240.0. You can select another netmask,
    as long as it minimally masks all bits that are given in the network