Lync Server 2013 provides the option to employ DNS load balancing in combination with hardware load balancing to split the incoming Lync server traffic across the two load-balancing mechanisms for an Enterprise pool. With this configuration, the HTTP traffic is load balanced using a hardware load balancer, whereas the SIP and media traffic is load balanced using DNS. To enable this functionality, a very specific DNS configuration is required. First, two DNS A records are used to resolve the fully qualified name of the pool to the IP address of each of the Front End servers. An additional DNS A record is then used to resolve the fully qualified name of the pool web components service to the virtual IP address of the load balancer. The following is a sample DNS configuration that leverages both DNS load balancing and hardware load balancing for an Enterprise pool:
EntFE1.companyabc.com A 10.1.1.2 Standard host record
EntFE2.companyabc.com A 10.1.1.3 Standard host record
LyncPool.companyabc.com A 10.1.1.2 DNS load balancing for SIP and media traffic
LyncPool.companyabc.com A 10.1.1.3 DNS load balancing for SIP and media traffic
LyncWeb.companyabc.com A 10.1.1.4 Hardware load balancing for HTTP traffic