System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP)

Using Fully Qualified Domain Names With LDAP

Unlike NIS or NIS+ clients, an LDAP client always returns a fully qualified domain name (FQDN) for a host name. The LDAP FQDN is similar to the FQDN returned by DNS. For example, suppose your domain name is the following:

Both gethostbyname() and getnameinfo() return the FQDN version when looking up the host name server:

Also, if you use interface-specific aliases such as server-#, a long list of fully qualified host names are returned. If you are using host names to share file systems or have other such checks, you must account for the checks. For example, if you assume non-FQDNs for local hosts and FQDNs only for remote DNS-resolved hosts, you must account for the difference. If you set up LDAP with a different domain name from DNS, the same host might end up with two different FQDNs, depending on the lookup source.