The introduction of Client Access Server role as MAPI end point Outlook uses to connect to a mailbox has prompted many organizations to consider load balancing internal clients for the first time. The introduction of a load balancer to provide fault tolerance and sharing of load to client access, when combined with using a product such as Forefront TMG or UAG to publish Exchange, when those products can also provide load balancing, can be a source of confusion. The most common question is whether Forefront TMG (Forefront UAG) should be used to publish Virtual IP address (VIP) created on load balancer, as shown in the diagram below, or whether a farm of CAS should be configured on Forefront TMG, and that used as the destination for the publishing rule.
This approach of publishing the load balancer itself has both advantages and some disadvantages. Continue here.