Like many universities, we use OpenLDAP for our central directory system. As you might guess, the hostname for this system is ldap.stanford.edu. This is actually a DNS pool, though. There are multiple machines offering the same service. There's ldap1.stanford.edu, ldap2.stanford.edu, ldap3 and so on.
When I configure a Mac to use an external directory system, it's usually our OpenLDAP directory. Using Directory Access.app in the Utilities folder (or the command line equivalent, dsconfigldap), I usually enter that hostname, ldap.stanford.edu. However, there are limitations to this.
At some point during configuration, the Mac connects to the DNS pool, gets sorted to one of the physical machines, does a forward name resolution, then uses that numerical IP address for subsequent connections.
Here's the rub: if the IP address of that specific host changes, things break.