If you are talking about the Load Balanced Environments - LDAP Cluster - "Forests" - Multiple Domains
Please review the below link for more insight.
It is kind of on the right track, I am trying to allow user access from 2 separate forests by means of LDAP. The documentation says I need to add an additional certificate, but I don't quite understand how that is going to allow a connection to my second forest? where do I specify the second set of LDAP credentials and base DN query for my second domain?