[This is pre-release documentation and subject to change in future releases. This topic's current status is: Milestone-Ready]

Topic Last Modified: 2010-07-19

Domain Name System (DNS) Load Balancing balances the network traffic that is unique to Microsoft Communications Server 2010, such as SIP traffic and media traffic. DNS load balancing is supported for Front End pools, Edge Server pools, Director pools, and standalone Mediation Server pools. A pool that is configured to use DNS load balancing must have two fully qualified domain names (FQDNs) defined: the regular pool FQDN that is used by DNS load balancing (for example, pool1.contoso.com) and that resolves to the physical IPs of the servers in the pool, and another FQDN for the pool’s Web services (for example, web1.contoso.com), which resolves to the virtual IP address of the pool. For more information about DNS Load Balancing, see DNS Load Balancing in the Planning documentation.

Before you can use DNS load balancing, you must:

  1. Override the internal web services pool FQDN.

  2. Create DNS A host records to resolve the pool FQDN to the IP addresses of all the servers in the pool.

To override internal web services FQDN

  1. From the Communications Server 2010 Beta Refresh program group, open Communications Server Topology Builder.

  2. From the console tree, expand the Enterprise Edition Front End pools node.

  3. Right-click the pool, click Edit Properties, and then click Web Services.

  4. Below Internal web services, select the Override FQDN check box.

  5. Type the pool FQDN that resolves to the physical IP addresses of the servers in the pool.

  6. Below External web services, type the external pool FQDN that resolves to the virtual IP addresses of the pool, and then click OK.

  7. From the console tree, select Communications Server 2010 (Beta Refresh), and then in the Actions pane, click Publish Topology.

To create DNS A Host Records for all internal pool servers

  1. For each Front End Server in your pool, create a DNS A Host record that maps the pool FQDN to the IP address of that Front End Server.

    For example, if you had a pool named pool1.contoso.com and three front-end servers, you would create the following DNS entries:

    FQDN Type Data


    Host A


    Host A


    Host A

    For details about creating DNS A Host records, see Configure DNS Host Records.