DNS Load Balancing

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:

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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