configuring multiple ldap servers

Hi, I want to understand in freeradius with rlm_ldap, Is it possible to configure multiple LDAP servers in Freeradius and the freeradius uses different LDAP server for different requests. Is it possible to add some kind of id in radius requests, so that freeradius makes use of that ID to choose which LDAP server can be used for that request. I am new to this freeradius. Please help me to get some understanding ?? We can configure one LDAP server in freeradius radiusd.conf ldap section?? but how to configure multiple LDAP servers and what is the purpose of filter id attribute in freeradius?? Thanks Jyothi