Both NIS and NIS+ perform some of the same tasks. NIS+, however, allows for hierarchical domains, namespace security, and other features that NIS does not provide. For a more detailed comparison between NIS and NIS+, see How NIS+ Differs From NIS.
You can use NIS in conjunction with NIS+ under the following principles and conditions:
Servers within a domain. While you can have both NIS and NIS+ servers operating in the same domain, doing so is not recommended for long periods. As a general rule, using both services in the same domain should be limited to a relatively short transition period from NIS to NIS+. If some clients need NIS service, you can run NIS+ in NIS-compatibility mode as explained in Solaris 1 Release and NIS-Compatibility Mode.
Subdomains. If the master server of your root domain is running NIS+, you can set up subdomains whose servers are all running NIS. (If your root domain master server is running NIS, you cannot have subdomains.) This might be useful in situations where you are moving from NIS to NIS+. For example, suppose your enterprise had separate, multiple NIS domains, possibly at different sites. Now you need to link them all together into a single, hierarchical multi-domain namespace under NIS+. By first setting up the root domain under NIS+, you can then designate the legacy NIS domains as sub-domains that continue to run NIS until it is convenient to switch them over to NIS+.
Machines within a domain.
If a domain's servers are running NIS+, individual machines within that domain can be set up to use either NIS+, NIS, or /etc files for their name service information. In order for an NIS+ server to supply the needs of an NIS client, the NIS+ server must be running in NIS-compatibility mode as described in Solaris 1 Release and NIS-Compatibility Mode.