The networking model changed significantly in Windows Server 2008 Failover Clustering. First, and foremost, when we start talking about networking in 2008 Failover Clusters we need to drop some of the older concepts that have been around for awhile. Probably the one that needs to go first is the concept of 'Private' network. This term no longer applies in W2K8. All networks detected by the cluster service, and hence the cluster network driver, are, by default, classified as 'mixed' networks and are automatically configured for use by the cluster. Here is a sample of the default configuration for a network in a cluster -
Whether the cluster gets to use this network or not for cluster related communications (e.g. health checking, GUM updates, etc....) is determined by the check box next to "Allow the cluster to use this network.". You will also note that the box is checked for "Allow clients to connect through this network." This is the default configuration provided the network interface supporting the network has a default gateway configured. So, no DG configured....no client access is allowed unless a cluster administrator changes the default setting in the Failover Cluster Management interface. Inspecting the cluster registry settings for this network, the 'Role' is set = 3 which is a 'Mixed' network. So, cluster either gets to use the network or it does not......no more 'Private' network.