Hardware Load Balancer Requirements for Lync Server 2010 - NextHop

Microsoft Lync Server 2010 supports both DNS load balanced and hardware load balanced solutions. While DNS load balancing can be used to distribute SIP traffic equally among the various Front End servers in a Front End pool, a hardware load balancer must be used to handle HTTP connections to Lync Web Services. Please note that a hardware load balancer is not required when a Lync Server 2010 Standard Edition or a single Lync Server 2010 Enterprise Edition Front End Server is deployed within a Lync environment. ...

Many customers are unaware of the hardware load balancing requirements for Lync Server 2010 when using source address affinity persistence for Lync Web Service requests, from both internal and external clients. Although source address affinity persistence may be sufficient for many Lync Web Services requests, the new mobility features available in Lync Server 2010 CU4 will require cookie-based persistence for external connections to Lync Web Services.    LINK