Clients configured on Solaris 9 or later Solaris software releases are fully compatible with directory servers set up to serve Solaris 8 clients, which only support version 1 profiles. However, to take advantage of newer features built into Solaris 9 and later releases, and to use the newer security model, you must use version 2 profiles.
Servers can serve a mix of both old and new clients. Clients see the same results from the server as long as schema mapping is not enabled and version 2 profiles are not configured to use special filters with the serviceSearchDescriptors attribute. Obviously if the server is not using the default schema, older clients cannot use that server as Solaris 8 clients cannot arbitrarily map nondefault schema.