You do not need to configure a private network for a single-node cluster.
Sun Cluster software uses the private network for internal communication between nodes. A Sun Cluster configuration requires at least two connections to the cluster interconnect on the private network. You specify the private-network address and netmask when you configure Sun Cluster software on the first node of the cluster. You can either accept the default private-network address (172.16.0.0) and netmask (255.255.0.0) or type different choices.
After the installation utility (scinstall, SunPlex Installer, or JumpStart) has finished processing and the cluster is established, you cannot change the private-network address and netmask. You must uninstall and reinstall the cluster software to use a different private-network address or netmask.
If you specify a private-network address other than the default, the address must meet the following requirements:
The address must use zeroes for the last two octets of the address, as in the default address 172.16.0.0. Sun Cluster software requires the last 16 bits of the address space for its own use.
The address must be included in the block of addresses that RFC 1918 reserves for use in private networks. You can contact the InterNIC to obtain copies of RFCs or view RFCs online at http://www.rfcs.org.
You can use the same private network address in more than one cluster. Private IP network addresses are not accessible from outside the cluster.
Sun Cluster software does not support IPv6 addresses for the private interconnect. The system does configure IPv6 addresses on the private network adapters to support scalable services that use IPv6 addresses. But internode communication on the private network does not use these IPv6 addresses.
Although the scinstall utility lets you specify an alternate netmask, best practice is to accept the default netmask, 255.255.0.0. There is no benefit if you specify a netmask that represents a larger network. And the scinstall utility does not accept a netmask that represents a smaller network.
See Planning Your TCP/IP Network in System Administration Guide, Volume 3 (Solaris 8) or Planning Your TCP/IP Network (Tasks), in System Administration Guide: IP Services (Solaris 9 or Solaris 10) for more information about private networks.