Using LDAP’s altServer on OS X Clients

Binding an OS X client to an LDAP server is pretty simple, but when it’s time to scale up, Apple wants us to use proxy servers and load balancers to offer failover and redundancy. This is by far the best approach, but sometimes setting up such a front-end for a cluster of servers is┬átime or cost prohibitive depending on the scope of the project and the size of your fleet. In this case, it would be easier to simply have the OS X clients authenticate to a single server, using a list of trusted replica servers as a failover for when that primary server is unreachable for any reason. RFC4512 defines a LDAP attribute called altServer, and we can use that attribute to configure exactly such a setup.