At first you need to create a casarray on Exchange 2010 Server or Servers.
Second: Configure Virtual Directories
Set Exchange 2010 Virtual Directories
Third: You set static RPC ports on your Client Access Server
Exchange 2010: Setting Static RPC ports when using a Kemp LoadMaster
Fourth: you register in DNS your casarray name and autodiscover name on a new “virtual” IP address.
Fifth: You configure the Kemp loadbalacers as descriptind in: LoadMaster Deployment Guide for MS Exchange 2010 with the new “virtual” IP address.
When a hardware load balancer based CAS array has been properly configured, all servers in the array are represented by a single virtual IP (VIP) address and a fully qualified domain name (FQDN). When a client request comes in, it will be sent to an Exchange 2010 CAS server in the CAS array using DNS round robin distribution method.