OpenLDAP 2.3.35
I know about the time limit on the search, but is there a user-specified one on the connect?
I ask because when our primary LDAP server went down for maintenance, the various applications took around 2-3 minutes before trying the secondary server (accompanied by much wailing and gnashing of teeth).
I would've thought that the fail-over would have been practically instantaneous (which it is if the server in question is also the client's host); perhaps we have an errant packet filter in the way, but that's beyond the scope of this list.