Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool queries the Win32_NetworkAdapter Microsoft Windows® Management Instrumentation (WMI) class to determine the value of the NetConnectionID key. If the value for the NetConnectionID key contains the string Internal, or HEART, it indicates that the interface is the cluster private (heartbeat) network.

The Exchange Server Analyzer also reads the following registry value to determine the link speed and duplex settings for the network interface card being used for the cluster heartbeat network:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\ <NetworkCardDeviceID> \SpeedDuplex

Additionally, the Exchange Server Analyzer also reads the following registry value to determine whether automatic network speed detection is enabled:


If the value for the 0 key contains the string AUTO, it indicates that automatic network speed detection is enabled.

If the Exchange Server Analyzer determines that both SpeedDuplex is set to 0 and automatic network speed detection is enabled for the cluster heartbeat network, a warning is displayed.

Communication between server cluster nodes is critical for smooth cluster operations. If you use a multiple speed Ethernet network adapter for cluster communications and configure the adapter to automatically detect the network speed, the adapter may cause problems within the cluster. During the detection process, packets cannot be handled by the adapter and must be queued. Some adapters may unintentionally trigger the automatic detection process to reoccur occasionally. Therefore, communications are queued and communication delayed. Delays of this kind may cause cluster nodes not to receive critical packets promptly and may cause premature failover of cluster resources. It is recommended that the heartbeat network in a cluster be manually set to 10 megabits and half-duplex. This configuration will provide sufficient bandwidth and reliable communication.

To correct this warning

  • Configure the heartbeat network interface card for a link speed of 10 megabits and a duplex setting of half-duplex. Because the configuration steps for each network card are different, follow the instructions from your hardware provider to correctly configure the heartbeat network. Configuring these options may require an updated driver.

For more information about the recommended settings for the private network in a Windows server cluster, see the Microsoft Knowledge Base article 258750, "Recommended Private 'Heartbeat' Configuration on a Cluster Server" (