This article introduces a hotfix that changes the IP address resource behavior in failover clustering to enable SQL Server availability groups support in Windows Server 2012. The hotfix lets you use the loopback adapters in failover clustering, and stops the piling of IP addresses to the networking stack. After you install the hotfix, the LoopbackAdapterAllowed registry entry is provided to enable or disable the hotfix functionality. To enable the hotfix functionality, set the REG_DWORD value of the LoopbackAdapterAllowed registry entry to 1. To disable the hotfix functionality, set the REG_DWORD value to 0. The registry entry is located under the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ClusSvc\Parameters