Within a network there must be at least one machine acting as a NIS server. You can have multiple NIS servers, each serving different NIS "domains" - or you can have cooperating NIS servers, where one is said to be the master NIS server, and all the other are so-called slave NIS servers (for a certain NIS "domain", that is!) - or you can have a mix of them...
Slave servers only have copies of the NIS databases and receive these copies from the master NIS server whenever changes are made to the master's databases. Depending on the number of machines in your network and the reliability of your network, you might decide to install one or more slave servers. Whenever a NIS server goes down or is too slow in responding to requests, a NIS client connected to that server will try to find one that is up or quicker.
NIS databases are in so-called DBM format, derived from ASCII
databases. For example, the files /etc/passwd and
/etc/group can be directly converted to DBM format using
ASCII-to-DBM translation software ("dbload", it's included with the
server software). The master NIS server should have both, the ASCII
databases and the DBM databases.
Slave servers will be notified of any change to the NIS maps, (via the "yppush" program), and automatically retrieve the necessary changes in order to synchronize their databases. NIS clients does not need to do this since they always talks to the NIS server to read the information stored in it's DBM databases.
The author of the YP clients for linux has informed us that the newest ypbind (from yp-clients.tar.gz) is able to get the server from a configuration file - thus no need to broadcast (which is insecure - due to the fact that anyone may install a NIS server and answer the broadcast queries...)