@André - I am not exactly sure what you mean. I have added the IP address of both ESX boxes as allowed initiators on the Server 2012 iSCSI target.
You can see in the attached screenshots that my second ESX box (with IP 10.100.0.3) found the target IP address. In the second screen you can see that the second ESX box doesn't show any LUNs when I try and add storage. In the third screen you see that I have added both the IP addresses of my ESX boxes to the list of allowed initiators on the Server 2012 iSCSI target.