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Q. What configuration must I perform for the NICs in my Windows Server 2003 cluster nodes?

A. You need at least two NICs for a cluster: one for the internal cluster communications (i.e., the heartbeat) and one for general (i.e., public) access by clients and administration. To configure the NICs for their specific uses, perform these steps:

  1. Start Cluster Administrator (Start, Programs, Administrative Tools, Cluster Administrator). Doing so should automatically open your existing cluster.
  2. Expand Cluster Configuration and select Networks.
  3. Right-click the NIC that will be used for internal communications and select Properties.
  4. On the General tab, which the Figure shows, select the "Internal cluster communications only (private network)" option and click OK.
  5. Repeat the process for the NIC that will be used for public communications; however, select the "All communications (mixed network)" option, which ensures that the cluster will continue performing its internal communications even if the internal communications NIC fails. (The mixed-network option is the Microsoft best-practice approach.) Although you could select the "Client access only (public network)" option, doing so would result in the cluster experiencing communications problems if the internal communications NIC failed.

If you have additional NICs installed in cluster nodes that you don't want to use for clustering, clear the "Enable this network for cluster use" check box in the properties of each NIC that you don't want to use.

Finally, within the cluster configuration, perform these steps to ensure that the internal NIC has a higher priority than the public NIC:

  1. Right-click the cluster name (the top or root object in the left pane of the Cluster Administrator console), then select Properties from the displayed context menu.
  2. Select the Network Priority tab.
  3. At the page that the Figure shows, make sure that the private, or heartbeat, NIC is at the top of the list box.
  4. Click OK.

You should also ensure that the correct Link Speed and Duplex has been configured for both the public and heartbeat NICs. For example, on the public NIC, you would typically use 100Mbps with full duplex (assuming this is how the switch is connected). For the heartbeat NIC, the Microsoft best practice is to use 10Mbps with half duplex. You can access the duplex settings via the Advanced tab of the network adapters properties as the figure shows.

The autosense mode of some 10/100 Ethernet adapters might automatically detect the speed of the connected network. However, during the detection process, packets can't be handled by the adapter and must be queued. Some adapters might inadvertently trigger the autodetection process to reoccur intermittently. As a result, communications are queued and delayed. Delays of this nature might cause cluster nodes not to receive critical packets in a timely fashion and might cause premature failover of cluster resources. This is why it's important to manually set the correct speed and duplex to avoid any possible autosense-related problems.

Also on the heartbeat NIC for the cluster you should disable the file and print sharing for networks client; client for Microsoft networks and NetBIOS over TCP/IP are disabled (and for Windows 2000 cluster nodes, disable DHCP media sense):

  1. Open up the heartbeat network adapter properties and select the General tab.
  2. Clear the "Client for Microsoft Networks" and the "File and Printer Sharing for Microsoft Networks" check boxes.
  3. Select the "Internet Protocol (TCP/IP) and click Properties.
  4. Ensure the IP address and subnet mask are set but that the default gateway and DNS are not configured.
  5. Click the "Advanced..." button.
  6. Select the "DNS" tab.
  7. Ensure the "Register this connection's addresses in DNS" is blank.
  8. Select the WINS tab.
  9. Under the NetBIOS setting, section select the "Disable NetBIOS over TCP/IP" option and click OK.
  10. Click OK twice more to close all open dialog boxes.

For more information on heartbeat card configuration, please see the Microsoft article " Recommended private "Heartbeat" configuration on a cluster server" at

Finally, you should configure the adapter bind order so that the public NIC has a higher priority than the private (heartbeat) NIC. To do so, open the Network Connections control panel applet, select "Advanced Settings..." from the Advanced menu, and under the "Adapters and Bindings" tab ensure the public has precedence over the heartbeat, as the figure If you have additional remote access connections these should be below the heartbeat NIC.

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