Jan 30 15:57:39 [NIT_LDAP 0x7f62287a9700]: QueryRootDomainName: Failed to Establish LDAP Connection for domain: xxx.yyy.zzz, error : -2

This error above comes up from my OES 2015 sp1 server after configuring NSS for AD to join the desired domain (which it did).
Port 389 is open and the server can connect to the port via telnet to the indicated.

Nitconfig get > displays correct info regarding domain, gc server/port and ldap port

bit of a mistery.
klist -k also shows the documented entries.