Direct traffic between Master LDAP and Peer LDAP

We need to setup two LDAP servers, one a master the other a peer master. This is so the master updates the peer master but should the master go down we can perform changes using the peer master. The problem is that all traffic needs to go to the master and let the master synch the peer master. Should the master go down, the peer master now becomes the master and all traffic needs to go to this server. When the original master is back on line, he is now the peer master not the main master. Does anyone have any inputs as to how this could be configured with the F5. Is an iRule the best approach or is there something better?