System Administration Guide: Naming and Directory Services (NIS+)

Starting with the Solaris 10 8/07 release, the Solaris OS does not have two separate hosts files. The /etc/inet/hosts file is now a single hosts file that contains both IPv4 and IPv6 entries. You need not maintain IPv4 entries in two hosts files that always require synchronization. For backward compatibility, the /etc/inet/ipnodes file is replaced with a symbolic link of the same name to the /etc/inet/hosts file. For more information, see the hosts(4) man page. NIS clients and servers can communicate using either IPv4 or IPv6 RPC transports.