This article was previously published under Q176320
This article contains information about the effects of a network adapter failure withina cluster and different ways the condition may be handled.
The impact of network adapter failure may vary depending on hardwareconfiguration and the number of network adapters installed. With manydifferent possible network configurations, this article covers the threemost common configurations.
Private Network, Client Network Configured for All Communications:
The Administrator's guide for Microsoft Cluster Server (MSCS) suggestsusing an isolated network for cluster communications and one adapter forthe client network (configured for both client and cluster communications).With this configuration, if the adapter fails for the private network thatthe cluster nodes use, the nodes may use the client network for theircommunications and still communicate.
If the client network adapter fails, the IP address resources bound forthat adapter will also fail. If the resources cannot be brought online, thegroup will failover to a surviving node in the cluster. Simply removing thenetwork cable from the client network adapter does not constitute anadapter failure.
If both adapters fail to the point that the cluster nodes cannotcommunicate, the arbitration process begins for access to the quorum disk.The winner of the process takes control of the cluster and its groups. Theloser withdraws from the cluster by shutting down its Cluster service.
Private Network, Client Network Configured for Clients Only:
MSCS handles this configuration very similarly to configuration 1 notedabove. However, if an adapter on the private network fails, there is noother network configured to allow for cluster communications. As a result,the cluster nodes will arbitrate for the quorum disk and the winner willtake control of all groups. The loser of the arbitration process willwithdraw from the cluster by shutting down its Cluster service.
No Private Network for Cluster Communications:
While this configuration works, it is further limited. If the adapter fails in one of the nodes, with no other adapter to use as an alternate for cluster communications, the nodes immediately arbitrate for the quorum disk. The winner of the arbitration process takes control of all cluster groups and the losing node shuts down its Cluster service. With no way for the two nodes to communicate, there is a possibility that the winning node may not have access to the client network, but won the arbitration process anyway. Because of the obvious limitation of this configuration, this method is not recommended or a supported configuration.
Note This is not a supported cluster configuration. As per the Microsoft Cluster Server Hardware Compatibility List (HCL), at least two network adapters must be present in each cluster node. One of those network adapters must be configured for private cluster communications exclusively. Microsoft recommends configurations similar to configuration 1 and 2 above.Configuration 2 is more desirable with an extra private network in addition to the one mentioned in the example. This allows for two private networks for cluster communications and provides the ability to keep all clustercommunications isolated. Private networks may be accomplished by the use of a crossover cable between nodes or by the use of isolated hubs. Configuration 3 may work but is not a supported HCL configuration.