Changing the IP Address of a Cluster Adapter May Result in Failover

Changing the IP address and subnet mask for a network adapter that is designated for internal use only may result in the inability of the nodes to communicate. This may manifest itself as an uncontrolled failover.

For example, assume that NODE-A is running and is the owner of all groups and Resources. When NODE-B is started, all the resources fail over to NODE-B. If you restart NODE-A, all the groups and resources fail over to NODE-A again.

When the IP address and subnet mask is changed, the Cluster service sees this as a new network adapter. If you check in the Cluster Administrator tool under Networks, you see a new adapter listed as "New Cluster Network." In some instances, this may mean that the cluster does not have a single network configured for internal use.

These instances may include:

• Changing the IP address and subnet mask of all adapters in both nodes.
• Having only one network adapter for all communications in the cluster.
• Having two networks; one configured for client access only and the other for internal communication only, and changing the IP address of the adapter designated for internal use.

To resolve this problem, follow these specific steps. Both adapters to be used for internal communication must be in the same subnet for this to work properly:

1. Power off the second node.
2. On the first node, ensure that the Cluster service is started, and then start Cluster Administrator.
3. In the left hand pane, open the Network folder. You see a list of the different network resources.
4. Right-click New Cluster Network, and then click Properties. Note that this is set to Use only for Client Access.
5. If this connection was originally used for all communications or internal cluster communications, configure the network for its original setting.
6. After you change the setting, power this node off.
7. Power on the second node and repeat the above steps to verify that the change was properly entered for the second node.
8. Power on the first node.
9. Verify in Cluster Administrator under Networks that the new adapter has a State setting of Up.
10. Right-click New Cluster Network, and click Rename, and then type a descriptive name for this adapter (for example "HeartBeat and Corporate Access").

The proper method for changing IP addresses on a cluster is to make the changes on one adapter at a time, making sure that the nodes have consistent access to a domain controller or are domain controllers themselves, and ensuring that the clusters always have at least one network that the nodes can use for communication.

For additional information about troubleshooting related issues, click the article numbers below to view the articles in the Microsoft Knowledge Base: