Originally posted on Clustering For Mere Mortals:
If you set up a multisite cluster (nodes in different subnets), you will find that by default the cluster enables RegisterAllProvidersIP cluster resource for its network name. This results in two entries in DNS for the SQL Cluster name resource, one for each cluster IP address. If you use the optional MultiSubnetFailover=True parameter in the connection string, clients will try both IP addresses simultaneously and connect to the first server that responds. For SQL Server Management Studio you add that setting under the additional Connections Parameters.