One of our customer used the following way to implement redundancy for multiple LDAP server on Sametime Community Server:
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This Sametime server has some strange setting in da.nsf and stconfig.nsf which have two LDAP documents to point to two Domino LDAP servers . These two Domino LDAP servers are in the same Domino Cluster and has the same directory data. The customer use these setting to implement redundancy for Domino LDAP.
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In current supported version of Sametime Community Server (9.0.x/10.0.x/11.x), the above way to implement redundancy for multiple LDAP server is not supported. Sametime only support this configuration when using a Load balancer.
But some customer think a load balancer need more cost and configuration is complicated, and wish Sametime could provide a simple way to implement redundancy for multiple LDAP server in future release.
For example, for a two LDAP server configuration, Sametime can provide some parameter to switch real connection from LDAP Server A to LDAP Server B if LDAP Server A is down.
You can implement Round Robin DNS for this, and set the respray interval to 5 minutes. It won't be a perfect solution, but should get you a single host to use for LDAP. This will not perform any kind of health check to know if a server is up or down. A network load balancer is the best way. The re-spray parameter and other best practices are described here: https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0081763