FreeIPA. It supports a lot of features, has a lot of documentation backed by Red Hat, and a fantastic mailing list that helps usually within hours. It also can

FreeIPA. It supports a lot of features, has a lot of documentation backed by Red Hat, and a fantastic mailing list that helps usually within hours. It also can create a 2-way trust with active directory if that is also desired. It has integration with multi-factor authentication too if desired. I've been running a several hundred user development environment with dozens of LDAP authenticated services, for about 4 years now. It has been great, the web UI works really nicely, and it has active development. I recommend it without hesitation. If you want further information, email anthonyclarka2 a.t. gmail.