This article will cover the installation of two OpenLDAP instances on different nodes. OpenLDAP will be configured to provide multi-master replication. Writes should still be sent to a single server, but both can be used for directory reads. In the event of failure of the write node, a load balancer or similar solution could fail writes over to the other node. OpenLDAP multi-master replication to me doesn’t seem like true multi-master replication, rather an active-active read LDAP database with hot standby of a write database. In this author’s opinion, (Oracle) Sun JDS and Forgerock OpenDJ offer far superior replication abilities.
This article will not cover OpenLDAP basics which you can already find within the administration guide available from OpenLDAP. Review the documentation available there before proceeding with this tutorial.