If you installed the Oracle Grid Infrastructure software on the nodes in your cluster, then you can enable the Windows Firewall only after adding certain executable files and ports to the Firewall exception list.
The Firewall exception list must be updated on each node.
Grid_home\bin\gpnpd.exe - Grid Plug and Play daemon
Grid_home\bin\oracle.exe - Oracle Automatic Storage Management (Oracle ASM) executable file (if using Oracle ASM for storage)
Grid_home\bin\racgvip.exe - Virtual Internet Protocol Configuration Assistant
Grid_home\bin\evmd.exe - OracleEVMService
Grid_home\bin\crsd.exe - OracleCRService
Grid_home\bin\ocssd.exe - OracleCSService
Grid_home\bin\octssd.exe - Cluster Time Synchronization Service daemon
Grid_home\bin\mDNSResponder.exe - multicast-domain name system (DNS) Responder Daemon
Grid_home\bin\gipcd.exe - Grid inter-process communication (IPC) daemon
Grid_home\bin\gnsd.exe - Grid Naming Service (GNS) daemon
Grid_home\bin\ohasd.exe - OracleOHService
Grid_home\bin\TNSLSNR.EXE - single client access name (SCAN) listener and local listener for Oracle RAC database and Oracle ASM
Grid_home\opmn\bin\ons.exe - Oracle Notification Service (ONS)
Grid_home\jdk\jre\bin\java.exe - JVM